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The Role of Water in Platinum‐Catalyzed Cycloisomerization of 1,6‐Enynes: A Combined Experimental and Theoretical Gas Phase Study
Author(s) -
Baumgarten Sigrid,
Lesage Denis,
Gandon Vincent,
Goddard JeanPhilippe,
Malacria Max,
Tabet JeanClaude,
Gimbert Yves,
Fensterbank Louis
Publication year - 2009
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.200900003
Subject(s) - cycloisomerization , chemistry , nucleophile , enyne , platinum , catalysis , carbene , alkyne , electrophile , double bond , medicinal chemistry , molecule , photochemistry , computational chemistry , stereochemistry , combinatorial chemistry , organic chemistry
Pt II ‐catalyzed cycloisomerization of a 1,6‐enyne proceeds quickly in CHCl 3 at room temperature, and also in the gas phase. However, calculations predict a slow reaction, because of the formation of a very stable chelate that undergoes oxidative cyclization at a high energy cost. The electrophilic activation of the alkyne followed by nucleophilic attack of the double bond to generate a cyclopropyl carbene would lead to a faster reaction, but the decomplexation of the double bond to generate an unsaturated platinum species is also energetically disfavored. However, decomplexation can be envisaged if an adventitious molecule of water enters the coordination sphere of the metal. This crucial role of water in Pt II ‐catalyzed cycloisomerization of enynes, initially sensed some years ago (Echavarren et al., J. Am. Chem. Soc. 2001 , 123 , 10511) is now supported by mass spectrometry studies.