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A practical synthesis of 2,3-dihydro-1,5-benzothiazepines

spectroscopy, SYNTHESIS

Dec 082017

A practical synthesis of 2,3-dihydro-1,5-benzothiazepines

Green Chem., 2017, 19,5703-5707
DOI: 10.1039/C7GC02097J, Paper

Domenico C. M. Albanese, Nicoletta Gaggero, Meng Fei
Hexafluoro-2-propanol as the solvent allows a catalyst free domino approach to 2,3-dihydro-1,5-benzothiazepines in up to 98% yield.

A practical synthesis of 2,3-dihydro-1,5-benzothiazepines

Domenico C. M. Albanese,^a Nicoletta Gaggero*^b and Meng Fei^b

*Corresponding authors

^aDepartment of Chemistry, Università degli Studi di Milano, via C. Golgi 19, Milano, Italy

^bDepartment of Pharmaceutical Sciences, Università degli Studi di Milano, via L. Mangiagalli 25, Milano, Italy
E-mail:nicoletta.gaggero@unimi.it

Domenico C. M. Albanese

University of Milan

LocationMilano, Italy

DepartmentDepartment of Chemistry

Positionassociate professor

Domenico Albanese received his Ph.D. degree in 1993 with Prof. Dario Landini working on phase transfer catalysis. After short stays at Imperial College London and the Technical University of Denmark, he gained a permanent position at the Università degli Studi di Milano, where he was appointed associate professor in 2008. His research interests include novel developments of phase-transfer catalysis, green chemistry and the development of new environmentally friendly antifouling agents.

University of Milan

image file: c4ra11206g-p2.tif

Nicoletta Gaggero

Nicoletta Gaggero received her Ph.D. degree in 1992 working on stereoselective reactions with natural proteins, enzymes and models of enzymes. After working at the Laboratoire de Chimie de Coordination du CNRS of Toulouse, she obtained a permanent position at the Università degli Studi di Milano. Her research interests cover the field of biocatalysis and asymmetric synthesis.

Abstract

2,3-Dihydro-1,5-benzothiazepines have been obtained through a domino process involving a Michael addition of 2-aminothiophenols to chalcones, followed by in situ cyclization. Up to 98% chemical yields have been obtained at room temperature under essentially neutral conditions by using hexafluoro-2-propanol as an efficient medium.

http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C7GC02097J?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

2,4-Diphenyl-2,3-dihydro-1,5-benzothiazepine (4a)

Yellow solid; mp 114-116 C [lit.1 , 114-115 °C], AcOEt/PE 1:9. 1H NMR (300 MHz, CDCl3,): 3.07 (t, J = 12.6 Hz, 1 H), 3.32 (dd, J = 4.7, 13.1 Hz, 1 H), 4.99 (dd, J = 4.5, 12.0 Hz, 1 H), 7.12-7.17 (m, 1 H), 7.25-7.30 (m, 5 H), 7.44-7.51 (m, 4 H), 7.62 (d, J = 6.1 Hz, 2 H), 8.06 (d, J = 7.5 Hz, 2 H). Isolated Yield: 339 mg, 86%.

2-(4-Hydroxyphenyl)-4-phenyl-2,3-dihydro-1,5-benzothiazepine (4e)

Light brown solid; mp 131-134 °C. AcOEt/PE 40:60.

1H NMR (CDCl3, 300 MHz):  = 3.01 (t, J = 12.7 Hz, 1 H), 3.28 (dd, J = 4.8, 12.9 Hz, 1 H), 4.95 (dd, J = 4.7, 12.5 Hz, 1 H), 5.10 (bs, 1 H), 6.76 (d, J = 8.5 Hz, 2 H), 7.18-7.21 (m, 3 H), 7.35 (d, J = 8.5 Hz, 1 H), 7.46- 7.55 (m, 4 H), 7.63 (dd, J =1.5, 7.7 Hz, 1 H), 8.06 (m, 2 H).

13C NMR (CDCl3, 75 MHz): 37.99 (CH2), 60.07 (CH), 115.53 (CH), 123.08 (C), 127.40 (CH), 128.79 (CH), 131.17 (CH), 136.54 (C), 141.59 (C), 155.24 (C). IR (KBr): 1599, 2921, 3350 cm-1 .

MS (ESI): m/z= 332.24 (MH)+ .

Anal. Calcd. for C21H17NOS: C, 76.10; H, 5.17; N, 4.23, found: C, 76.21; H, 5.15; N, 4.24.

Isolated Yield: 360 mg, 87%.