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Cesium ( Z )‐2‐Carbomethoxyethenethiolate: A Reagent for the Preparation of ( Z )‐2‐Carbomethoxyethenyl Thioethers Including Selected Cysteine and Homocysteine Derivatives
Author(s) -
O'Donnell Jennifer S.,
Singh Suneel P.,
Metcalf Thomas A.,
Schwan Adrian L.
Publication year - 2009
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.200801025
Subject(s) - chemistry , reagent , electrophile , caesium , base (topology) , substitution reaction , alkyl , electrophilic substitution , enantiomer , conjugate , cysteine , medicinal chemistry , combinatorial chemistry , organic chemistry , catalysis , mathematical analysis , mathematics , enzyme
As a means to circumvent the standard and sometimes troubling conjugate addition reaction of thiols to alkyl propiolates, a new reagent, cesium ( Z )‐2‐carbomethoxyethenethiolate, is introduced. The cesium carbonate mediated methanolysis of ( Z )‐2‐carbomethoxyethenyl thiolacetate at low temperature creates cesium ( Z )‐2‐carbomethoxyethenethiolate in solution. For base‐insensitive and solvolytically stable electrophiles, efficient substitution can be achieved by direct introduction to the electrophile. The conditions were adapted to accommodate base‐sensitive cysteine derivatives, and the use of DMF as a cosolvent permits the isolation of ( Z )‐2‐carbomethoxyethenyl cysteinyl thioethers in high enantiomeric purity (>99:1 er ) and with good Z / E ratios. There was no evidence of carbon substitution reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)