Construction of Alkenyl‐Functionalized Spirocarbocyclic Scaffolds from Alkyne‐Containing Phenol‐Based Biaryls via Sequential Iodine‐Induced Cyclization/Dearomatization and Pd‐Catalyzed Coupling of N‐Tosylhydrazones

Abstract

of main observation and conclusion An efficient strategy for the formation of alkenyl-functionalized spirocarbocyclic scaffolds from alkyne-containing phenol-based biaryls via sequential iodine-induced cyclization/dearomatization and Pd-catalyzed coupling of N-tosylhydrazones is developed. The approach provides various spirocarbocyclic compounds in moderate to excellent yields with good functional tolerance. The results also demonstrate the feasibility for the direct cross-couplings of N-tosylhydrazones with sterically congested tetrasubstituted alkenyl halides.

Cationic [1,5]‐Aryl Migrations of Propargyl Benzyl Ethers – A Stereospecific Approach to E‐ and Z‐Tetrasubstituted Olefins

“…Initially, the halonium ion [X + ] interacts with the alkyne in propargylbenzyl ether 1/3/7 and induces the nucleophilic attack by the arene of the benzyl ether part. The ipsonucleophilic attack of the arene in a 6-endo-dig fashion, [12] generates the spirocyclic carbocation intermediate 6, which is nothing but phenonium ion. This 6 may undergo the ring-opening through the cleavage of the spiro CÀ C bond (at benzyl carbon) via the assistance of oxygen-atom to give 8, which upon reaction with water give a hemiacetal 9.…”

Recent Advances in Transition‐Metal‐Catalyzed Reactions of N‐Tosylhydrazones

“…An elaborated example for the use of N ‐tosylhydrazones was presented by the group of Wang who reported the construction of alkenyl‐functionalized spirocarbocyclic scaffolds from N ‐tosylhydrazones and alkyne‐containing phenol‐based biaryls (Scheme 40). [63] This approach, which proceeds via sequential iodine‐induced cyclization and palladium catalyzed coupling of N ‐tosylhydrazones, demonstrated the applicability of direct cross‐couplings of N ‐tosylhydrazones with sterically congested and more sophisticated tetrasubstituted alkenyl halides.…”

A Facile Construction of Bisheterocyclic Methane Scaffolds through Palladium‐Catalyzed Domino Cyclization

“…[13][14] For instance, domino reactions have been extensively developed for the synthesis of biologically useful benzofuran scaffolds (Scheme 1a). [13b,15] Inspired by these previous studies as well as a continuation of our efforts to develop novel reaction methodologies for the synthesis of heterocyclic derivatives through cascade reactions, [16] we report herein a facile and convenient palladium-catalyzed domino cyclization reaction between allyl ether and o-ethynylphenol, providing various bis(benzofuranyl)methane scaffolds. Significantly, one C(sp 2)-O bond, two C(sp 2)-C(sp 3) bonds as well as two benzofuran rings are formed in a single synthetic sequence (Scheme 1b).…”