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Facial Selectivity in the Diels–Alder Reactions of 2,2‐Disubstituted Cyclopent‐4‐ene‐1,3‐dione Derivatives and a Computational Examination of the Facial Selectivity of the Diels–Alder Reactions of Structurally Related Dienes and Dienophiles
Author(s) -
Liu PeiYing,
Wu YongJin,
Pye Cory C.,
Thornton Paul D.,
Poirier Raymond A.,
Burnell D. Jean
Publication year - 2012
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.201101301
Subject(s) - chemistry , selectivity , steric effects , bicyclic molecule , cyclopentene , ene reaction , heptane , octane , diels–alder reaction , stereochemistry , medicinal chemistry , organic chemistry , catalysis
The facial selectivity in the Diels–Alder reactions via endo transition states of the plane‐nonsymmetric dienophiles spiro[bicyclo[2.2.2]octane‐2,1′‐[3]cyclopentene]‐2′,5′‐dione ( 6 ) and spiro[bicyclo[2.2.1]heptane‐2,1′‐[3]cyclopentene]‐2′,5′‐dione ( 7 ) has been found to be very similar to the facial selectivity of reactions of cyclopentadienes fused to bicyclo[2.2.2]octane and bicyclo[2.2.1]heptane ( 4 and 5 ). This is strong evidence for steric control in their facial selectivities. Density functional computations involving the reactions of these compounds, as well as a series of conformationally locked model addends ( 26a – c and 27a – c ), revealed geometrical and energetic properties that confirmed that the facial selectivity is governed by steric effects. Steric interactions appeared to be the reason for the low endo / exo selectivity of dienophiles 6 , 7 , 2,2‐dimethylcyclopent‐4‐ene‐1,3‐dione ( 20 ), and spiro[5.4]dec‐8‐ene‐7,10‐dione ( 23 ).