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Theoretical elucidation of the rhodium‐catalyzed [4 + 2] annulation reactions
Author(s) -
Geng CaiYun,
Li JiLai,
Huang XuRi,
Liu HuiLing,
Li Zhuo,
Sun ChiaChung
Publication year - 2007
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20824
Subject(s) - annulation , chemistry , steric effects , regioselectivity , rhodium , alkyne , catalysis , reaction mechanism , computational chemistry , selectivity , model system , combinatorial chemistry , medicinal chemistry , stereochemistry , organic chemistry
The reaction mechanism of the Rh‐catalyzed [4 + 2] annulation of 4‐alkynals with isocyanates is unraveled using density functional calculations. The reaction mechanisms of the model system and the real substituted system have been investigated and the results are compared. From our theoretical results based on the model and real substituted system, it is shown that (a) the rate‐determining step is the Rh‐H addition to the alkyne, (b) the formation of the cyclopentenone G and glutarimide K represents a severe competition, and (c) the product selectivity should be controlled by the amount of the isocyanates. In addition, it is demonstrated that there exist steric effects in the real substituted system, but missed in model system. Our calculations also show that although the results obtained on the model system could explain the mechanism in principle, the real substituted system could reflect the mechanism more exactly and make the reaction proceed with regioselectivity. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008