Quantum Chemical Characterization of Cycloaddition Reactions between the Hydroxyallyl Cation and Dienes of Varying Nucleophilicity
Cramer, C. J.; Barrows, S. E.
J. Org. Chem.
1998, 63, 5523.
Hydroxyallyl cation prefers to undergo cycloaddition reactions with dienes in a stepwise fashion. Analysis of positive charge distribution in the intermediate formed after initial C-C bond formation provides a simple unifying method for rationalizing changes in reactivity as a function of diene nucleophilicity. Predicted product distributions are consistent with results from experimental studies. Interestingly, for the initial intermediate generated from 1,3-butadiene, [3+2] cycloaddition reactions are favored, but closure to form a C-O bond as the second step results in an intermediate that can undergo a low-energy Claisen rearrangement to form a 7-membered ring product identical to that expected from compact [4+3] cycloaddition.
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