A case of highly diastereoselective addition to unsymmetrical ketones: lk ‐addition of (2‐alkenyl)triphenoxytitanium derivatives

(2‐Butenyl)‐, (4‐methyl‐2‐pentenyl)‐, and (2‐heptenyl)triphenoxytitanium ( 2a – c ) add to dialkyl, alkyl aryl‐, and alkinyl aryl ketones to give high yields of tertiary homoallylic alcohols ( 5 – 12 ), which are diastereomerically enriched up to 98%. Configurational assignment by degradation of two of the products to olefins 15 and 18 ‐ through β‐hydroxy acids 13 and 16 and β‐lactones 14 and 17 ‐ leads to the proposal of a general mechanism and of a specification of the relative topicity lk of the process ( Scheme 5 ). The allylic Ti‐compounds 2 can serve as d 2 ‐reagents (see the d 2 ‐synthon II and the aldol‐type structures 1 ).