The Aldol‐Grob Reaction: Regioselective Synthesis of (E)‐Alkenes from Aldehydes and Ketones with Ytterbium Triflate Catalysis

Abstract

A simple, good yielding and solvent-free aldol-Grob reaction sequence, catalysed by Yb(OTf) 3 hydrate, affording (E)-alkenes regioselectively from aldehydes and ketones is described.

Oxetane Intermediate during a Direct Aldol Reaction: Stereoselective [5 + 1] Annulation Affording Tetralines

“…Aldol-lactonization yielding β-lactones 2 was straightforward evidence of the oxetane intermediate because the oxetane framework remained in the β-lactone product without its ring opening . The contribution of oxetane intermediates has also been proposed for the tandem aldol–Grob reaction, , which led to the carboxylic acid R 1 CO 2 H and the alkene R 2 CHCHR 3 .…”

“…Oxetane is occasionally proposed as an intermediate during aldol reactions (Scheme ). − Oxetane intermediates 1 were successfully detected via NMR monitoring of the Mukaiyama aldol reaction but were readily converted to the usual aldol products . Aldol-lactonization yielding β-lactones 2 was straightforward evidence of the oxetane intermediate because the oxetane framework remained in the β-lactone product without its ring opening .…”

“…The reaction pathway may compete with conventional aldol condensation, leading to an enone product. Alternatively, the benzyl cation intermediate can be generated via the oxetane intermediate, which has been established as an intermediate during the aldol–Grob tandem reaction …”

Ytterbium(III) Triflate-Catalyzed Conversion of Carbonyl Compounds into 1,3-Oxathiolanes in Ionic Liquids

“…Lanthanide triflates are versatile Lewis acids and they have been employed in a number of organic reactions. 9 Ytterbium(III) triflate Yb(OTf) 3 was first used by Forsberg et al 10 and since then it has found a wide utility in organic synthesis especially in deprotection of acetates, 11 Michael and Diels-Alder reactions, 12 aldol-Grob reaction, 13 imino ene reaction, 14 detritylation, 15 electrophilic substitution and cyclization, 16 and isomerization of glycidic esters. 17 Ionic liquids, particularly those based on the 1,3-dialkylimidazolium cation have gained considerable interest as reaction media in recent years, 18 often permitting easier catalyst recycling.…”