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A case of highly diastereoselective addition to unsymmetrical ketones: lk ‐addition of (2‐alkenyl)triphenoxytitanium derivatives
Author(s) -
Seebach Dieter,
Widler Leo
Publication year - 1982
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19820650704
Subject(s) - chemistry , synthon , allylic rearrangement , aldol reaction , aryl , reagent , alkyl , medicinal chemistry , stereochemistry , organic chemistry , catalysis
(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 ).