A new heteroannulation method to 2-cyclohexenone, mediated by phosphonate auxiliaries. Synthesis of 4,5,6,7-tetrahydrobenzothiazole derivatives
摘要:
Dimethyl (1,2-epoxy-3-oxocyclohex-1-yl)phosphonate 7, easily available from 2-cyclohexen-1-one, affords the new (tetrahydrobenzothiazolyl)phosphonates 10 upon reaction with thiocarboxamides 8. This cyclocondensation proceeds with regioselective conjunction of the bis-nucleophile 8 to carbonyl group and adjacent oxirane carbon of the epoxide precursor. On treatment with alkali the 5,6-dihydro-7(4H)benzothiazolones 12 are obtained from compounds 10, or from the intermediately formed bicyclic dihydroxy derivatives 9. Reaction of the corresponding cyclopentylphosphonate 14 with thiobenzamide (8b) yields the cyclopentathiazole derivative 15 as a single isomer, the dihydro-thiazole moiety being now annulated regio- and cis-stereoselectively to both oxirane carbons of the epoxyphosphonate.
Versatile approaches to a library of building blocks based on 5-acylthiazole skeleton
作者:Olesia G. Kulyk、Dmytro A. Biloborodov、Maksim A. Cherevatenko、Yevhen Y. Shyriakin、Alexander Yu. Lyapunov、Alexander V. Mazepa、Valerii V. Vashchenko、Valeriy D. Orlov、Maksim A. Kolosov
DOI:10.1080/00397911.2020.1808224
日期:2020.12.1
Abstract Thiazole derivatives represent an important class of azole heterocycles with a broad spectrum of biological activity and, therefore, the synthesis of these compounds is of remarkable concern. We present here practical and reliable protocol for synthesis of some 5-acylthiazoles and demonstrate their utility in the preparation of several new series of thiazole-containing building blocks through