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

✍ Scribed by Dieter Seebach; Leo Widler

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: German
• Weight: 572 KB
• Volume: 65
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19820650704

✦ Synopsis

Abstract

(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).