The Aldol Reaction of Allenolates with Aldehydes in the Presence of Magnesium Diiodide (MgI 2 ) as Catalyst

Stereoselective synthesis of ( Z )‐ α ‐(hydroxyalkyl)‐ β ‐iodoacrylates (=(2 Z )‐2‐(hydroxyalkyl)‐3‐iodoprop‐2‐enoates) was achieved in a one‐pot coupling reaction from methyl prop‐2‐ynoate, Me 3 SiI, and an alkanal under mild conditions with MgI 2 as catalyst (→ 1 – 9 ; see Table and Scheme 1 ). Baylis‐Hillman β ‐iodo adducts were generated in excellent yields with high ( Z )‐selectivity. The conversion of methyl prop‐2‐ynoate to an active methyl 3‐iodo‐1‐[(trimethylsilyl)oxy]allenolate intermediate in situ followed by carbonyl addition is proposed as the reaction sequence ( Schemes 1 and 2 ).