Premium
Synthesis of cis‐Hedione ® and Methyl Jasmonate via Cascade Baylis–Hillman Reaction and Claisen Ortho Ester Rearrangement
Author(s) -
Chapuis Christian,
Büchi George H.,
Wüest Hans
Publication year - 2005
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.200590248
Subject(s) - chemistry , claisen rearrangement , allylic rearrangement , ketone , carroll rearrangement , cascade reaction , stereoselectivity , stereochemistry , organic chemistry , catalysis
The exocyclically unsaturated conjugated keto esters 10 , obtained via a Claisen ortho ester rearrangement of the allylic hydroxy ketones 9 , were either directly hydrogenated or partially isomerized into the endocyclically unsaturated tetrasubstituted didehydrojasmonoid intermediates 14 , prior to a more selective hydrogenation with Pd/C in cyclohexane to the disubstituted oxocyclopentaneacetates 15 ( Scheme 2 ). The key intermediates 9 were obtained either by a four‐step sequence, including acetal protection/deprotection from enone 1 , in the specific case of hydroxy ketone 9a ( Scheme 1 ), or more directly and generally by a Baylis–Hillman reaction from cyclopent‐2‐en‐1‐one ( 16 ) and the appropriate aldehydes 17 ( Scheme 2 ). The judicious choice of these aldehydes opens versatile modifications for the stereoselective introduction of the partially cis ‐ or epimerized trans ‐C(2) jasmonoid side chain, while the Baylis–Hillman reaction, catalyzed by chiral [1,1′‐binaphthalene]‐2,2′‐diols (BINOLs) 19 ( Scheme 3 ), may be efficiently conducted in a one‐pot cascade fashion including the ortho ester Claisen rearrangement.