Issue 46, 2017

A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

Abstract

Alkynyl sulfonamides undergo sequential 1,4- then 1,2-addition/rearrangement with lithium acetylides to yield enediynes in the absence of any promoters or catalysts. Mechanistic investigations suggest that the reaction proceeds via 1,4-conjugate addition of the nucleophile to the unsaturated system to give a key alkenyl lithium species which is stabilised by an intramolecular coordination effect by a sulfonamide oxygen atom. This species can be considered a vinylidene carbenoid given the carbon atom bears both an anion (as a vinyllithium) and a leaving group (the sulfonamide). The intramolecular coordination effect serves to stabilise the vinyllithium but activates the sulfonamide motif towards nucleophilic attack by a second mole of acetylide. The resulting species can then undergo rearrangement to yield the enediyne framework in a single operation with concomitant loss of aminosulfinate.

Graphical abstract: A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

Supplementary files

Article information

Article type
Paper
Submitted
29 Sep 2017
Accepted
23 Oct 2017
First published
20 Nov 2017
This article is Open Access
Creative Commons BY license

Org. Biomol. Chem., 2017,15, 9895-9902

A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

T. O. P. Hayes, B. Slater, R. A. J. Horan, M. Radigois and J. D. Wilden, Org. Biomol. Chem., 2017, 15, 9895 DOI: 10.1039/C7OB02437A

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