Access to 1,4‐Thiazepanes via Gold‐Catalyzed 7‐exo‐dig Thioallylation and their Cycloisomerization to Bicyclic [4.3.1] Bridgehead‐Olefinic Systems

Abstract

A series of 1,4-thiazepanes were synthesized using gold-catalysis from 1,3-aminothioethers having two or three carbon stereocenters. The process consists in a 7-exo-dig cyclization with CÀ S bond formation and concomitant allyl S-to-C migration, which occurs intramolecularly as demonstrated by a cross-over experiment. X-ray crystal-structure analysis of one product confirmed the expected stereochemistry. Two examples of reactions, azide-alkyne cycloaddition (CuAAC) and N-alkylation, illustrate the potential postfunctionalization of the synthesized 1,4-thiazepanes. Finally, the N-propargyl 1,4-thiazepanes underwent a sulfur-assisted 1,6-enyne cycloisomerization, which led through a 6-exo-dig cyclization to N,Sheterobicyclo[4.3.1] systems with a bridgehead double bond.

Gold(I)‐Catalyzed Carbothiolation via Rearrangement of S‐Propargyl Group: An Access to 3‐Allenyl or 3‐Indenyl Benzo[b]thiophenes

“…The reported migrating groups are trialkylsilyl, α‐alkoxy alkyl, allyl, and p ‐methoxybenzyl. This strategy was applied for the synthesis of various 5‐ and 6‐membered S‐containing heterocycles, [4] and recently our group reported the gold(I)‐catalyzed 7‐ exo ‐dig carbothiolation with allyl S‐to‐C migration to access 7‐membered N,S‐heterocycles [5] . Surprisingly, there are no examples of S‐propargyl sulfides involved in this type of transformation [6] .…”

“…This strategy was applied for the synthesis of various 5-and 6-membered S-containing heterocycles, [4] and recently our group reported the gold(I)-catalyzed 7-exo-dig carbothiolation with allyl S-to-C migration to access 7-membered N,S- heterocycles. [5] Surprisingly, there are no examples of S-propargyl sulfides involved in this type of transformation. [6] We report herein the gold-catalyzed synthesis of 3-allenyl benzo[b]thiophenes 2, starting from ortho-alkynyl S-propargyl phenyl sulfides 1 (Scheme 1, R = propargyl) via a [3,3]-sigmatropic Claisen rearrangement of propargyl vinyl sulfonium intermediate.…”