Chemistry of allene sulphoxides: a new methodology for the synthesis of spiroketals and 1,5-dioxadecalin ring systems

Abstract

A n e w method for the construction of 1,5-dioxadecalins and spiroketals which utilises acid o r base catalysed intramolecular additions of alcohols t o allene sulphoxides is described.

Chemistry of spiroketals

“…equilibrates to a single equatorial methyl isomer 177 at C15 of the closed system. This pioneering simplification was used by Nakahara95 some years later in a dithiane-based approach to calcimycin in which the two diastereomers represented by 179 cyclized to a single C15 isomer 180 in 66% yield.…”

A New Entry to Oxacycles via Base-Catalyzed Endo Mode Cyclization of Allenyl Sulfoxides and Sulfones

“…These would be expected to undergo endo mode cyclization at the sp-hybridized carbon center, if these allenyl derivatives have a suitable δ-hydroxy appendage at the C-1 position − …”

From Allylic Sulfoxides to Allylic Sulfenates: Fifty Years of a Never-Ending [2,3]-Sigmatropic Rearrangement

“…The versatile reactivity of allenyl sulfoxides and their easy access from propargylic sulfenates using [2,3]-sigmatropic rearrangement have made them ubiquitous synthetic intermediates that evolve through desulfinylation with n -BuLi, desulfinylation by electrophilic addition of iodine to the allene, α-deprotonation followed by alkylation, γ-deprotonation, , chelotropic addition of SO 2 , and Michael nucleophilic additions to the allene central carbon of amines, alcohols, sulfides, and dimethyl cuprate . In particular, allenyl sulfoxides 468 and 474 , prepared from propargylic alcohols 467 and 472 , respectively, contain internal nucleophiles and provide simple access to heterocyclic structures such as spiroketals 470 and indoles 475 (Scheme ). …”