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Claisen Rearrangements of Allylic and Propargylic Alcohols Prepared by an N ‐Boc‐2‐acyloxazolidine Methodology − Application to the Synthesis of Original Chiral Building Blocks
Author(s) -
Agami Claude,
Couty François,
Evano Gwilherm
Publication year - 2002
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(20021)2002:1<29::aid-ejoc29>3.0.co;2-b
Subject(s) - enantiopure drug , chemistry , epimer , claisen rearrangement , moiety , stereoselectivity , aldehyde , stereochemistry , amide , allylic rearrangement , intramolecular force , organic chemistry , enantioselective synthesis , catalysis
Stereodefined alkenols prepared in two steps from a Weinreb amide derived from ( R )‐phenylglycinol undergo highly stereoselective Claisen rearrangements. The masked aldehyde moiety of the produced N ‐Boc‐alkenyloxazolidines can then be recovered and reduced without epimerization, to yield new enantiopure chiral building blocks. Alternatively, epoxidation of these N ‐Boc‐2‐alkenyloxazolidines by a well‐established intramolecular bromocarbamation involving the Boc protecting group occurs stereoselectively. The resulting α,β‐epoxyoxazolidines are then transformed into trisubstituted stereodefined cyclopropanes. Claisen rearrangements of propargylic alcohols, on the other hand, stereoselectively give α‐allenyloxazolidines. These compounds follow a different pathway to α‐alkenyloxazolidines as regards bromocarbamation. An original route to enantiopure 3‐hydroxy‐4‐phenylpiperidine was found in the course of this study.