Titanium(IV) Chloride-Mediated Carbon−Carbon Bond-Forming Reaction between 3,3-Dialkylcyclobutanones and Aldehydes

Treatment of 3,3-dialkylcyclobutanones with titanium(IV) chloride in the presence of aldehyde gave β′-chloro-β-hydroxy ketones in high yields. It was speculated that ring cleavage of the cyclobutanone ring with titanium(IV) chloride gave trichlorotitanium enolate having a tertiary alkyl chloride moiety and then aldol reaction of the titanium enolate proceeded. A trialkylsilylmethyl group at the 2-position of cyclobutanone facilitated the ring cleavage. Synthesis of substituted cyclopentenone from an obtained product is also described.