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One‐Pot Vinylation of Azlactones: Fast Access to Enantioenriched α‐Vinyl Quaternary Amino Acids
Author(s) -
Serra Massimo,
Bernardi Eric,
Marrubini Giorgio,
Colombo Lino
Publication year - 2017
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.201700353
Subject(s) - chemistry , oxazolone , moiety , enantioselective synthesis , organic chemistry , combinatorial chemistry , aldol reaction , aryl , stereochemistry , catalysis , alkyl
We report a fast one‐pot protocol for the direct vinylation of azlactones [oxazol‐5‐(4 H )‐ones] by using as a key step an aldol addition with 2‐(phenylselenenyl)acetaldehyde followed by dehydroxyselenation. The acid hydrolysis of the oxazolone ring gave the desired fully deprotected α‐vinyl quaternary α‐amino acids in almost quantitative yields. An enantioselective variant of the method was also developed by using catalytic chiral bases. The use of Sharpless ligand (DHQD) 2 PHAL produced the final quaternary amino acids in good overall yields (62–78 %) and with ee values up to 86 %. Scaling up the optimized protocol to gram quantities did not affect the yields and ee values. We also demonstrated that the vinyl moiety installed onto the oxazolone ring can be exploited as a handle for the attachment of aryl groups through a Heck coupling reaction.