One‐Pot Synthesis of 6,7‐Fused Steroidal Thiazoles in Cholestane Series

Abstract

A convenient one-pot synthesis of 2¢-amino-and 2¢-N-phenylamino-5a-cholest-6-eno[6,7-d]thiazole derivatives 4-9 are reported. The synthesis involves the reaction of cholestan-6-ones 1-3 with thiourea or phenylthiourea and iodine. The products have been characterized on the basis of IR, 1 H-NMR and Mass, which find support in two cases from comparison with authentic samples.

Heterocycle‐bridged and Conformationally Constrained Retinoids: Synthesis of 4‐(7,8,9,10‐Tetrahydro‐7,7,10,10‐tetramethyl‐4H‐benzo[6,7]chromeno‐ [4,3‐d]thiazole‐2‐yl)benzoic Acid

“…13,14 As precursor 2, 3,6,7,8,9-hexahydro-6,6,9,9-tetramethylbenzo[g]chromen-4-one (17) were a synthesized as outlined in Scheme 1. At the first, the related diol (11) was converted to di-chloro-analog (12) by using concentrated hydrochloric acid saturated with hydrogen chloride gas in room temperature.…”

“…Friedel-crafts dialkylation of phenol with compound 12 in the presence of AlCl 3 was used for preparing compound 13 in good yield. For chromanone ring construction from phenolic compound (13), three different routes were attempted: (i) nucleophilic substitution of 3-bromopropionic acid in the presence of NaH and DMF followed by cyclization with PPA; (ii) addition to acrylonitrile using NaOMe as a base and subsequent cyclization with H 2 SO 4 under heating; (iii) acylation reaction with 3-chloropropionic acid in the presence of trifluoromethane sulfonic acid (TFMSA), followed by interamolecular nucleophilic substitution using aqueous NaOH as a base. Best result was achieved using the latter method with 41% overall yield.…”

A Facile Synthesis of 6,7-Fused Steroidal Thiazoles via 1,3-Intramolecular Migration of Bromine/Allylic Displacement of Bromine

“…10 Due to the significance of thiazole derivatives in medicinal chemistry, considerable effort has been devoted to develop alternate routes for their synthesis. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Although several strategies with variable yields have been reported for the synthesis of steroidal as well as non-steroidal thiazoles, the Hantzsch's protocol [29][30][31] continues to be a method of choice involving the reaction of α-halocarbonyl compound with an appropriate thiourea or thioamide. Thus, we have also selected the Hantzsch's protocol for this purpose, 5-bromosteroidal ketones, [32][33] are selected instead of 7-bromosteroidal ketones because both lead to the same product but preparation of 7-bromocholestan-6-one [20][21] is much more tedious leading to a mixture of products.…”