AUTHOR OF THIS BLOG

DR ANTHONY MELVIN CRASTO, WORLDDRUGTRACKER

Total CCl4 guest alignment in a quasiracemic clathrate closely related to Dianin’s compound

 polymorph  Comments Off on Total CCl4 guest alignment in a quasiracemic clathrate closely related to Dianin’s compound
Oct 092017
 

 

CrystEngComm, 2017, 19,5703-5706
DOI: 10.1039/C7CE01275F, Communication
Christopher S. Frampton, James H. Gall, David D. MacNicol
In the trigonal CCl4quasiracemic clathrate, space group R3, formed from host components S-(-)-Dianin’s compound, 4, and its (+)-2R,4R 2-nor methyl analogue, 2, the unprecedented complete ordering of a C-Cl bond of the guest with respect to the c-axial direction and the participation of an unexpected host conformation is reported for the first time.

Total CCl4 guest alignment in a quasiracemic clathrate closely related to Dianin’s compound

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Abstract

Single crystal X-ray analysis at 100 K reveals that in the trigonal CCl4quasiracemic clathrate, space group R3, formed from host components S-(−)-Dianin’s compound and its (+)-2R,4R 2-nor methyl analogue there is an unprecedented complete ordering of a C–Cl bond of the guest with respect to the c-axial direction. In this clathrate and that formed from the (+)-2R,4R and (+)-2R,4S epimers the participation of an unexpected host conformation is reported for the first time.

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A green route for methanol carbonylation

 spectroscopy, SYNTHESIS  Comments Off on A green route for methanol carbonylation
Oct 092017
 

 

Catal. Sci. Technol., 2017, Advance Article
DOI: 10.1039/C7CY01621B, Paper
Youming Ni, Lei Shi, Hongchao Liu, Wenna Zhang, Yong Liu, Wenliang Zhu, Zhongmin Liu
Halide-free and noble metal-free pyridine-modified H-mordenites exhibit high stability and selectivity in methanol carbonylation to acetic acid.

A green route for methanol carbonylation

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Abstract

Acetic acid is one of the most important bulk commodity chemicals and is currently manufactured by methanol carbonylation reactions with rhodium or iridium organometallic complexes and halide-containing promoters named Monsanto or BP Cativa™ homogeneous processes, respectively. Developing a halide-free catalyst and a heterogeneous process for methanol carbonylation is of great importance and has recently attracted extensive research attention. Here, we report a green route for direct synthesis of acetic acid via vapor-phase carbonylation of methanol with a stable, selective, halide-free, and noble metal-free catalyst based on pyridine-modified H-mordenite zeolite. Methanol conversion and acetic acid selectivity can reach up to 100% and 95%, respectively. Only little deactivation is observed during the 145 hour reaction.

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A Fully Continuous-Flow Process for the Synthesis of p-Cresol: Impurity Analysis and Process Optimization

 PROCESS, spectroscopy, SYNTHESIS  Comments Off on A Fully Continuous-Flow Process for the Synthesis of p-Cresol: Impurity Analysis and Process Optimization
Oct 092017
 

Abstract Image

A fully continuous-flow diazotization–hydrolysis protocol has been developed for the preparation of p-cresol. This process started from the diazotization of p-toluidine to form diazonium intermediate. The reaction was then quenched by urea and subsequently followed by a hydrolysis to give the final product p-cresol. Three types of byproducts were initially found in this reaction sequence. After an optimization of reaction conditions (based on impurity analysis), side reactions were eminently inhibited, and a total yield up to 91% were ultimately obtained with a productivity of 388 g/h. The continuous-flow methodology was used to avoid accumulation of the highly energetic and potentially explosive diazonium salt to realize the safe preparation for p-cresol.

 

STR1STR2

1H NMR (400 MHz, (CD3)2SO) δ/ppm: 9.06 (br s, 1H, −OH), 6.94 (d, J = 8.0 Hz, 2H, Ar–H), 6.62 (d, J = 8.0 Hz, 2H, Ar–H), 2.17 (s, 3H, −CH3).

13C NMR (CDCl3) δ/ppm: 153.0, 129.9, 115.1, 20.5.

 

Literature data:(3b) 1H NMR (300 MHz, CDCl3) δ/ppm: 7.03 (d, J = 8.2 Hz, 2H), 6.73 (dd, J = 8.2, 2.0 Hz, 2H), 4.75 (s, 1H, OH), 2.27 (s, 3H, CH3).

13C NMR (CDCl3) δ/ppm: 153.2, 130.2, 115.2, 20.6.

3(b) TaniguchiT.ImotoM.TakedaM.NakaiT.MiharaM.IwaiT.ItoT.MizunoT.NomotoA.OgawaA. Heteroat. Chem. 201526411– 416 DOI: 10.1002/hc.21275

A Fully Continuous-Flow Process for the Synthesis of p-Cresol: Impurity Analysis and Process Optimization

National Engineering Research Center for Process Development of Active Pharmaceutical Ingredients, Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Key Laboratory for Green Pharmaceutical Technologies and Related Equipment of Ministry of Education, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou 310014, P. R. China
Org. Process Res. Dev., Article ASAP
DOI: 10.1021/acs.oprd.7b00250
*Tel.: (+86)57188320899. E-mail: pharmlab@zjut.edu.cn.

http://pubs.acs.org/doi/full/10.1021/acs.oprd.7b00250

 

NMR PREDICT

STR1 STR2

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Sustainable chemistry: how to produce better and more from less?

 Uncategorized  Comments Off on Sustainable chemistry: how to produce better and more from less?
Oct 072017
 

 

Sustainable chemistry: how to produce better and more from less?

Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC02006F, Perspective
P. Marion, B. Bernela, A. Piccirilli, B. Estrine, N. Patouillard, J. Guilbot, F. Jerome
This review describes the rapid evolution of chemistry in the context of a sustainable development of our society. Written in collaboration between scientists from different horizons, either from public organizations or chemical companies, we aim here at providing recommendations to accelerate the emergence of eco-designed products on the market.

Sustainable chemistry: how to produce better and more from less?

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Abstract

The International Symposium on Green Chemistry (ISGC) organized in 2013, 2015 and 2017 has gathered many senior and young talented scientists from all around the world (2200 attendees in three editions), either from academia or industry. Through outstanding conferences, communications, debates, and round tables, ISGC has been the witness of the rapid evolution of chemistry in the context of a sustainable development of our societies, not only at the scientific and industrial levels but also on education, networking and societal aspects. This critical review synthesizes the different points of view and the discussions having taken place at ISGC and gives a general picture of chemistry, including few scientific disciplines such as catalysis, processes, resource management, and environmental impact, among others, within the framework of sustainable development. This critical review, co-authored by researchers from public organizations and chemical companies (small, medium and large industrial groups) provides criteria and recommendations which, in our view, should be considered from the outset of research to accelerate the emergence of eco-designed products on the market.

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Conclusions

Sustainable chemistry is the only mean to generate performant  products and long lasting  solutions able  to  generate  business  and  profit  for  chemical  industry.  Performance  is  the  best  systemic answer for customer needs and our societies. Defining  sustainable  chemistry  is,  however,  far  to  be  an  easy  task  because chemistry is a highly dynamic system. The sustainability of a value chain is for instance directly depending on the access  to energy (and above all to its origin – coal, gas, biomass…) and  on the supply of raw materials. In the current economic context,  it could be not so easy to predict what will be the best source of  energy or raw materials for a desired product in the future. The  development  of  predictive  tools  is  now  essential  and  will  represent probably one of the next scientific challenges in the coming years.  During the last 20 years, utilization of renewable feedstocks in  chemical processes has become a strategy of growing interest  but  it  definitely  does  not  guarantee  the  establishment  of  a  sustainable  chemistry.  Indeed,  in  some  cases,  it  is  more  sustainable to produce a chemical from a fossil carbon source  using decarbonized energy than the reverse. It is very important  to  distinguish  the  carbon  found  in  the  final  product  from  the  carbon content corresponding to the energy which is required  the  product  production  (going  from  raw  materials  to  manufacturing,  end  of  life,  etc.).  In  this  area,  the  concept  of biorefinery can help  to secure developments and  to minimize  investments  in  production  plant  by  mutualizing  facilities  and  R&D initiatives. Cooperation with local producers can also be a valuable  way  to  implement  new  bio‐based  products  while  favouring sustainable agricultural practices.  Whatever  the  raw materials  (renewable or  fossil), a complete  and systemic life cycle analysis of the whole chain value (from resources  to  manufacturing,  use  and  end  of  life)  must  be  performed because it gives us an accurate picture of the overall  economic,  environmental  and  societal  performances  of  a  product in an application for a defined market. In general, one should never forget that sustainable chemistry should help the  society to produce more and better (products).   Emergence of sustainable innovations on the market takes a lot  of  time  because  chemists  have  to  reinvent  chemistry.  To  achieve our  transition  to a sustainable society, we must  think  differently  and  bring  together  the  worlds  of  finance,  manufacturers, researchers and public authorities. The current  method of funding of research and innovation is not satisfying  yet because  too often based on  short‐term  projects and with  high Technology Readiness Level. Governments have to realize  that  this  funding  method  slows  down,  and  sometime  also  hampers, the emergence of future sustainable innovations.   Evolution of regulations with the aim of banning toxic, eco‐toxic  or  poor  biodegradable  products  is  an  important  driver  for  sustainable innovation. It is now seen and shared as a positive sign  providing  opportunities  to  develop  systemically  better  solutions  and  allowing  chemical  companies  advocating  sustainable development and products as a must to stay in the  competition.  As  examples,  ban  of  CFC,  replacement  of  chlorinated  or  other  toxic  solvents,  substitution  of  endocrine  disruptors lead to better solutions for the global benefit of our  societies.  Improving  public  perception  and  awareness  on  sustainable  chemistry is on the way but more efforts will be needed in the  future  to  definitely  contribute  to  the  emergence  of  eco‐ designed chemicals on the market.

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Below  we  provide  a  bulleted  list  to  summarize  the  main  recommendations that are, in our views, essential for designing sustainable products.  (1) Products  design  &  Manufacture:  For  the  intended  application, sustainable chemicals must imperatively bring a  global  benefit,  created  by  a  scientific  or  technological  breakthrough,  while  minimizing  risks.  They  should  also  generate profit to emerge on the market. Products should  be  produced  according  to  the  12  principles  of  green  chemistry. In addition, their end of life should be integrated  at the outset of research,  (2) Resources: They should be available for future generations  and  should  have  low  environmental  impact  (protecting  endangered species, deforestation, erosion of biodiversity,  contamination of natural resources, global warming, etc.), it  should  make  progress  the  societal  development  of  concerned area (sharing any benefits with local producer, no  child  labour,  help  developing  countries,  etc.)  and  their  utilization  should not destabilise other  supply  chains. Non  edible raw material, a return to the idea of ‘localness’ and  the need for closeness should be preferred,  (3) Process:  The  ideal  process  would  be  a  low  Capex  or  a  progressive  Capex  process and  should  be energy‐efficient,  not  use  solvents,  be  without  effluents,  should  limit  the  number of reactional and purification steps and should be  developed  rapidly  to  limit  the  associated  risks  and  costs.  Efforts  are  still  needed  for  miniaturisation  of  equipment,  intensification and development of continuous reactors,  (4)  Energy:  The  chemical  industry  is  also  energy  intensive.  Although  less  than  10%  of  fossil  carbon  is  used  for  the  manufacture of chemicals, finding decarbonized sources of  energy  is  mandatory  to  avoid  the  depletion  of  carbon  reserves  and  price  increase  and  to  ensure  that  future  generations  will  have  access  to  the  same  resource  in  the  same amount,   (5)  Life cycle assessment: it should be assessed in all cases, the  earlier the better, by preferring a ‘cradle to grave’ approach. It should give an accurate picture of the overall economic,  environmental and societal performances of a product in an  application for a defined market,  (6)  Education:  we  should  improve  public  awareness  and  perception  on  sustainable  chemistry  to  facilitate  the  acceptation of sustainable products by the consumer. More  education  programs  should  be  launched  in  the  future  not  only to reassure the consumer but also to create a pool of  students  better  armed  to  tackle  the  future  challenges  of  (sustainable)  chemistry.  The  rapid  development  of  digital  tools should be helpful to address this issue,  (7) Network: we should prefer working in an open innovation  mode  by  bringing  together  the  worlds  of  finance,  manufacturers,  researchers  and  public  authorities  to  accelerate the emergence of eco‐designed chemicals on the  market. Networks  should enable local  players  to adapt  to  changes  in  their  environment  while  optimising  their  economic and environmental efficiency,  (8)  Funding:  A  good  balance  between  funding  to  applied  research and basic research must be addressed in order to continuously  generate  scientific  innovation.  However,  public authorities must  realise  that societal challenges are  more  important  than  the  short  term  financial  challenges  faced  by  businesses.  The  current  model  of  our  economy  based  on  rapid  profitability  is  unfortunately  not  well  adapted  for  these  advances  since  long‐term  investments  will be needed for a more sustainable development of our  society,  (9)  Legislation & Regulation: it should facilitate the emergence  of sustainable chemicals by banning harmful chemicals  for  the  human  health  and  the  environment,  even  those  nowadays  generating  substantial  profits.  The  registration  process  of  improved  sustainable  chemicals  by  the  concerned agencies should be quicker than now to speed up  their integrations on the market,  (10)  Predictive  methods:  the  development  of  tools  to  accurately  predict  the  technical  and  application  performances, the economic efficiency, the environmental  and societal performance of a  targeted product should be  developed  to  limit  the  risks  and  costs  associated  with  potential  failure  and  to  reassure  the  investors.  It  is  also  urgent  to  develop  these  tools  for  chemicals  that  are  intended to be dispersed in nature.
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Total synthesis of natural products viairidium catalysis

 SYNTHESIS  Comments Off on Total synthesis of natural products viairidium catalysis
Sep 292017
 

 

Total synthesis of natural products via iridium catalysis

Org. Chem. Front., 2017, Advance Article
DOI: 10.1039/C7QO00664K, Review Article
Changchun Yuan, Bo Liu
An overview of the highlights in total synthesis of natural products using iridium as a catalyst is given

http://pubs.rsc.org/en/Content/ArticleLanding/2017/QO/C7QO00664K#!divAbstract

Total synthesis of natural products viairidium catalysis

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Abstract

Catalysis with transition metals is a powerful synthetic tool for achieving a high degree of molecular complexity from relatively simple building blocks. Among these transition metals employed, iridium has attracted significant attention owing to its multifold roles in catalysis of various synthetically significant methodologies, and thus iridium catalysts are widely used in natural product synthesis. This review aims to comprehensively summarize recent accomplishments in total synthesis of natural products using iridium as the catalyst.

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Image result for School of Chemical Engineering and Technology, North University of China, Taiyuan 030051, PR ChinaImage result for School of Chemical Engineering and Technology, North University of China, Taiyuan 030051, PR China

School of Chemical Engineering and Technology, North University of China, Taiyuan 030051, PR China

Image result for College of Chemistry, Sichuan University, Chengdu

Image result for College of Chemistry, Sichuan University, Chengdu

Image result for College of Chemistry, Sichuan University, ChengduKey Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, Sichuan University, Chengdu

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Photochemical intramolecular amination for the synthesis of heterocycles

 FLOW CHEMISTRY, flow synthesis  Comments Off on Photochemical intramolecular amination for the synthesis of heterocycles
Sep 272017
 

 

Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC02261A, Communication
Shawn Parisien-Collette, Corentin Cruche, Xavier Abel-Snape, Shawn K. Collins
Polycyclic heterocycles can be formed in good to excellent yields via photochemical conversion of the corresponding substituted aryl azides under irradiation with purple LEDs in a continuous flow reactor.

Photochemical intramolecular amination for the synthesis of heterocycles

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Abstract

Polycyclic heterocycles can be formed in good to excellent yields via photochemical conversion of the corresponding substituted aryl azides under irradiation with purple LEDs in a continuous flow reactor. The experimental set-up is tolerant to UV-sensitive functional groups while affording diverse carbazoles, as well as an indole and pyrrole framework, in short reaction times. The photochemical method is presumed to progress through a mechanism differing from the other methods of azide activation involving transition metal catalysis.

STR1

Methyl 9H-carbazole-2-carboxylate (9): Following the Photodecomposition Procedure A, starting from Methyl 2’-azido-[1,1’-biphenyl]-4-carboxylate, the crude mixture was purified by silica gel column chromatography (100 % hexanes → 10 % ethyl acetate in hexanes), to afford the desired product as a white solid (24.3 mg, 72 % yield). Following the Photodecomposition Procedure B, starting from Methyl 2’-azido-[1,1’- biphenyl]-4-carboxylate, the crude mixture was purified by silica gel column chromatography (100 % hexanes → 10 % ethyl acetate in hexanes), to afford the desired product as a white solid (27.7 mg, 82 % yield). NMR data was in accordance with what was previously reported.16

16 Takamatsu, K.; Hirano, K.; Satoh, T.; Miura, M. Org. Lett. 2014, 16, 2892-2895

NEXT…………..

STR2 str3

4-Isopropyl-9H-carbazole (14): Following the Photodecomposition Procedure A, starting from 2-azido-2’-isopropyl-1,1’-biphenyl, the crude mixture was purified by silica gel column chromatography (100 % hexanes → 10 % ethyl acetate in hexanes), to afford the desired product as a yellow solid (16.6 mg, 53 % yield). Following the Photodecomposition Procedure B, starting from 2-azido-2’-isopropyl-1,1’-biphenyl and using ethyl acetate as the solvant, the crude mixture was purified by silica gel column chromatography (100 % hexanes → 10 % ethyl acetate in hexanes), to afford the desired product as a yellow solid (16.0 mg, 51 % yield).

1H NMR (400 MHz, DMSO-d6) δ = 11.29 (s, 1H), 8.11 (d, J = 8.1 Hz, 1H), 7.50 (d, J = 8.1 Hz, 1H), 7.39-7.31 (m, 3H), 7.19- 7.15 (m, 1H), 7.08-7.03 (m, 1H), 3.92-3.82 (m, 1H), 1.41 (d, J = 6.8 Hz, 6H);

13C NMR (100 MHz, DMSO-d6) δ = 143.9, 140.3, 140.1, 126.0, 125.2, 122.8, 122.2, 119.9, 119.1, 114.9, 111.2, 108.9, 30.2, 22.8 (2C);

HRMS (ESI) m/z calculated for C15H15N [M-H]- 208.1130; found 208.1126.

///////////http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C7GC02261A?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

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Catalyst-free multi-component cascade C-H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines

 spectroscopy, SYNTHESIS  Comments Off on Catalyst-free multi-component cascade C-H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines
Sep 202017
 

 

Catalyst-free multi-component cascade C-H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines

Green Chem., 2017, 19,4036-4042
DOI: 10.1039/C7GC01494E, Communication
Mohit L. Deb, Choitanya D. Pegu, Paran J. Borpatra, Prakash J. Saikia, Pranjal K. Baruah
Synthesis of 1,3-oxazines via catalyst free C-H functionalization using molecular oxygen in water.

Catalyst-free multi-component cascade C–H-functionalization in water using molecular oxygen: an approach to 1,3-oxazines

 Author affiliations

Abstract

Herein, catalyst-free 3-component reactions of naphthols, aldehydes, and tetrahydroisoquinolines to synthesize 1,3-oxazines is reported. The reaction is performed in H2O in the presence of O2 as the sole oxidant at 100 °C, which proceeds through the formation of 1-aminoalkyl-2-naphthols followed by selective α-C–H functionalization of tert-amine.

15-phenyl-7a,12,13,15-tetrahydronaphtho[1′,2′:5,6][1,3]oxazino[2,3- a]isoquinoline (4a):1

White solid; Yield 61 %, 221 mg;

1H NMR (500 MHz, CDCl3): δ 7.79-7.77 (m, 1H), 7.74 (d, J = 8.9 Hz, 1H), 7.43-7.41 (m, 1H), 7.33-7.28 (m, 8H), 7.24-7.19 (m, 3H), 7.11 (d, J = 8.9 Hz, 1H), 5.65 (s, 1H), 5.44 (s, 1H), 3.40-3.26 (m, 2H), 3.12-3.09 (m, 1H), 2.90- 2.86 (m, 1H);

13C NMR (125 MHz, CDCl3): δ 151.9, 142.3, 135.0, 133.0, 132.4, 129.3, 129.1, 128.9, 128.8 (2C), 128.7, 128.6, 128.2, 127.4, 126.5, 126.2, 123.1, 122.7, 118.9, 110.9, 82.2, 62.6, 45.4, 29.4;

HRMS (ESI) exact mass calculated for C26H21NO [M+H]+ : 364.1701; found: 364.1705.

The representative procedure for the synthesis of 4a is as follows: 2-naphthol (1a, 144 mg, 1 mmol), benzaldehyde (2a, 106 mg, 1 mmol), tetrahydroisoquinoline (3, 133 mg, 1 mmol) and water (1.5 mL) were added in a round-bottom flask equipped with a magnetic stirring bar and a reflux condenser. The whole apparatus was efficiently flushed with oxygen gas and then connected to a balloon filled with oxygen. After vigorous stirring at 100 oC for 12 h, water was removed under vacuum and purified the reaction mixture by column chromatography (100-200 mesh silica gel, hexane-ethyl acetate) to obtain the product 4a as white solid. The other 1,3-oxazines were synthesized and purified by following the procedure described above

str4

STR7str6

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Efficient route for the construction of polycyclic systems from bioderived HMF

 spectroscopy, SYNTHESIS  Comments Off on Efficient route for the construction of polycyclic systems from bioderived HMF
Sep 162017
 

 

Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC02211E, Paper
F. A. Kucherov, K. I. Galkin, E. G. Gordeev, V. P. Ananikov
Efficient one-pot synthesis of tricyclic compounds from biobased 5-hydroxymethylfurfural (HMF) is described using a [4 + 2] cycloaddition reaction.

Efficient route for the construction of polycyclic systems from bioderived HMF

 Author affiliations

Abstract

The first synthesis of tricyclic compounds from biobased 5-hydroxymethylfurfural (HMF) is described. The Diels–Alder reaction was used to implement the transition from HMF to a non-planar framework, which possessed structural cores of naturally occurring biologically active compounds and building blocks of advanced materials. A one-pot, three-step sustainable synthesis in water was developed starting directly from HMF. The reduction of HMF led to 2,5-bis(hydroxymethyl)furan (BHMF), which could be readily involved in the Diels–Alder cycloaddition reaction with HMF-derived maleimide, followed by hydrogenation of the double bond. The described transformation was diastereoselective and proceeded with a good overall yield. The applicability of the chosen approach for the synthesis of analogous structures containing amine functionality on the side chain was demonstrated. To produce the target compounds, only platform chemicals were used with carbohydrate biomass as the single carbon source.

Endo-4,7-bis(hydroxymethyl)-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindole-1,3(2H)-dione (endo-4,7-bis(hydroxymethyl)norcantharimid-5-ene), 3

1H NMR (DMSO-d6) = 10.82 (s, 1H), 6.37 (s, 2H), 5.11 (t, 2H, J = 5.7 Hz), 3.97 (dd, 2H, J = 5.7 Hz, 12.8 Hz), 3.84 (dd, 2H, J = 5.7 Hz, 12.8 Hz), 3.44 (s, 2H);

13C NMR (DMSO-d6) = 176.9, 136.0, 92.1, 59.8, 48.8 ppm.

m/z HRMS (ESI) Calcd. for C10H11NO5 [M+Na]: 248.0529. Found 248.0536.

STR7

str4 str6

1H NMR PREDICT

 

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str4 str6

13C NMR PREDICT

 

str4 str6

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O=C1NC(=O)[C@H]3[C@@H]1[C@]2(C=C[C@]3(CO)O2)CO

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Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen

 spectroscopy, SYNTHESIS  Comments Off on Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen
Sep 072017
 

Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen

Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC02014G, Communication
Yanjun Xie, Xiangui Chen, Zhen Wang, Huawen Huang, Bing Yi, Guo-Jun Deng
Aerobic cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen under metal-free conditions.

Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen

 

http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C7GC02014G?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

Abstract

Metal-free oxidative cyclization for the one-pot synthesis of benzo[d]imidazo[2,1-b]thiazoles from 2-aminobenzothiazoles and cyclic ketones is described. Elemental sulfur combined with molecular oxygen as the benign co-oxidant was found to be unique and highly effective to promote this transformation without the aid of any metal salts. Various cyclic ketones smoothly reacted with 2-aminobenzothiazoles to give functional benzo[d]imidazo[2,1-b]thiazoles in good to very high yields, which thereby demonstrated the synthetic convergence of this methodology.

Graphical abstract: Metal-free oxidative cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen
7,8,9,10-Tetrahydrobenzo[d]benzo[4,5]imidazo[2,1-b]thiazole (3a)
White solid; yield: 39.2 mg (86%), mp 140-142 °C.
STR1
1H NMR (400 MHz, CDCl3, ppm) δ 7.67-7.62 (m, 2H), 7.38 (t, J = 7.76 Hz, 1H), 7.27 (t, J = 7.68 Hz, 1H), 3.07-3.04 (m, 2H), 2.77-2.74 (m, 2H), 2.00-1.95 (m, 2H), 1.92-1.86 (m, 2H);
13C NMR (100 MHz, CDCl3, ppm) δ 145.1, 142.4, 132.9, 129.7, 125.5, 123.9, 123.5, 121.8, 111.9, 24.8, 22.8, 22.7, 21.8;
MS (EI) m/z (%) 228, 200 (100), 160, 108, 51;
HRMS calcd. for: C13H13N2S + (M+H)+ 229.07940, found 229.07941.
 STR2
str3
PREDICT
STR1
STR2
cas 325766-28-7
C13 H12 N2 S, 228.31,  Benzimidazo[2,​1-​b]​benzothiazole, 7,​8,​9,​10-​tetrahydro-

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C1CCCc2c1nc3sc4ccccc4n23

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