Efficient Chirality Transfer in the SmI₂-Mediated Cyclization of Aldehydo β-Alkoxyvinyl Sulfoxides:  Asymmetric Synthesis of 3-Hydroxyoxanes

Abstract

Stereoselective syntheses of 3-hydroxyoxanes were achieved via efficient chirality transfer in the SmI2-mediated cyclization reactions of aldehydo beta-alkoxyvinyl sulfoxides.

Expedient Synthesis of (−)‐Amphidinolide X

“…Three other possible stereoisomers were also obtained by changing the double‐bond stereochemistry and the sulfoxide chirality. In comparison with the results obtained previously,4 a subtle change in the structure of the substrate (from a hydrogen atom to a methyl group) triggered a dramatic change of stereospecificity. The method described in this communication opens up new and rational ways for the preparation of functionalized oxacycles, particularly those derived from tertiary alcohols.…”

“…The structures of the major products may be predicted on the basis of the double‐bond stereochemistry and the sulfoxide configuration (sulfoxide chirality control). The observed stereospecificity appears to be totally unrelated to the data previously obtained for substrates derived from secondary alcohols 4. The results of SmI 2 ‐mediated 5‐ exo cyclizations of aldehydo β‐alkoxyvinyl sulfoxides prepared from secondary and tertiary alcohols are presented in Scheme .…”

“… Comparison of the cyclization products from β‐alkoxyvinyl sulfoxides derived from secondary (the previous study)4 and tertiary alcohols (the present work). Bn: benzyl.…”

“…We intended to obtain the key structural element A through 5‐ exo cyclization of aldehydo β‐alkoxyvinyl sulfoxide B (Scheme ). It is known4 that 5‐ exo cyclizations of aldehydo β‐alkoxyvinyl sulfoxides derived from secondary alcohols proceed under carbinol chirality control, and cis ‐2,5‐disubstituted oxolanes are formed regardless of the sulfoxide chirality. For ( E )‐ and ( Z )‐β‐alkoxyvinyl sulfoxides derived from tertiary alcohols, will the reactions proceed under sulfoxide or carbinol chirality control?…”

Air‐Stable Bifunctional Allylation Reagents for the Asymmetric Synthesis of Differentiated syn‐ and anti‐1,3‐Diols

“…To highlight the powerful synthetic utility of I and the asymmetric aldehyde allylation/Ir I -catalyzed allylic etherification strategy, we elected to synthesize 2,5-disubstituted 3alkoxytetrahydrofurans, which are core structural motifs in many biologically important molecules. [15] Despite numerous synthetic advancements, [16] methods/strategies that allow for the asymmetric synthesis of all stereoisomers of 2,5-disubstituted 3-alkoxytetrahydrofurans by means of reagent/catalyst control of the reaction stereochemistry have not been reported. [17] Scheme 3 describes a concise asymmetric synthesis of 2,5-disubstituted 3-alkoxytetrahydrofuran ring systems.…”