Gold/Acid‐Cocatalyzed Regiodivergent Preparation of Bridged Ketals via Direct Bis‐Oxycyclization of Alkynic Acetonides

Abstract

Abstract:The regioselective metal/acid co-catalyzed direct bis-oxycyclization of alkynyldioxolanes allows the efficient synthesis of optically pure biand tricyclic bridged acetal systems.

Stereoselective synthesis of higher homologues of pantolactone from (R)-glyceraldehyde acetonide

“…The intermediates 5 and 6 in turn could be achieved from the diastereomeric hydroxyalkenes 7 and 8, prepared from the (R)-glyceraldehyde acetonide 9 by allylation reaction with prenyl bromide. Following the above retrosynthetic analysis, (R)-glyceraldehyde acetonide 9 13 was subjected to indium-mediated allylation reaction 14 with prenyl bromide to furnish the diastereomeric hydroxyalkenes 7 15 and 8 in a 9:1 ratio as revealed by GC analysis 16 (Scheme 2). The two isomers were separated by column chromatography and characterized by spectral analysis.…”

Gold-catalyzed C–O bond forming reactions for the synthesis of six-membered O-heterocycles

“…The alkynyl-β-lactams by direct bisheterocyclization afforded optically pure tricyclic bridged acetals containing a 2-azetidinone nucleus with regiocontrolled Au/ Bronsted acid co-catalyst [266,267]. The desired ketal was produced when terminal alkyne was treated with gold(III) chloride/p-toluenesulfonic acid catalytic system.…”

Applications of metal and non-metal catalysts for the synthesis of oxygen containing five-membered polyheterocylces: a mini review

“…Ketals are crucial targets and important key structures in organic synthesis [199][200][201]. Fused, bicyclic and spiroketals are recurring moieties in natural compounds, and their synthesis is a key step in many total preparations.…”