slracine

A comprehensive study of a diastereoselective Rh‐catalyzed cyclization of terminal and internal allenols is reported. The methodology allows the atom economic and highly syn ‐selective access to synthetically important 2,4‐disubstituted, respectively 2,4,6‐trisubstituted tetrahydropyrans (THP). Furthermore, its utility and versatility is demonstrated by a great functional group compatibility and the enantioselective total synthesis of (‐)‐centrolobine.

S‐directed: An iridium‐catalyzed direct alkynylation for the indole C4‐ and C7‐positions was achieved with the assistance of sulfur directing groups. The transformation shows broad functional‐group tolerance with complete site selectivity, and the directing group can be either easily removed or transformed after the reaction.

Abstract

Indoles and their analogues have been one of the most ubiquitous heterocycles during the past century, and extensive studies have been conducted to establish practical synthetic methods for their derivatives. In particular, selective functionalization of the poorly reactive benzenoid core over the pyrrole ring has been a great challenge. Reported herein is an iridium‐catalyzed direct alkynylation of the indole C4‐ and C7‐positions with the assistance of sulfur directing groups. This transformation shows a wide range of functional‐group tolerance with exceptional site selectivity. The directing group can be either easily removed or transformed after catalysis. The synthetic utility of the alkyne fragment is demonstrated by the derivatization into the core structure of natural indole alkaloids.