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Straightforward Synthesis of α‐Substituted Prolines by Cross‐Metathesis
Author(s) -
Lumini Marco,
Cordero Franca M.,
Pisaneschi Federica,
Brandi Alberto
Publication year - 2008
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/ejoc.200800044
Subject(s) - chemistry , metathesis , yield (engineering) , lewis acids and bases , salt metathesis reaction , selectivity , organic chemistry , stereochemistry , combinatorial chemistry , catalysis , polymerization , polymer , materials science , metallurgy
The synthesis of several α‐substituted N ‐Boc‐protected prolines has been achieved by cross metathesis (CM) of N ‐Boc‐allylproline 5 with terminal long chain alkenes and alkenes bearing hydroxy, silyloxy, ester, and O ‐acetylglucosamido groups. The CM occurred with good selectivity and short reaction time under microwave heating conditions, affording yields in the range of 40–92 %. Addition of Ti(O i Pr) 4 as a Lewis acid allowed a slight increase of the yield in the case of alkenes with Lewis basic substituents. The CM was also successfully applied to allylproline protected with trichloroacetaldehyde 4 , but the intermediate products were less practical for further deprotection and elaboration. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)