Efficient photocyclization of o-alkylbenzaldehydes in the solid state: direct observation of E-Xylylenols en route to benzocyclobutenols

Narasimha Moorthy, J. ; Mal, Prasenjit ; Natarajan, R. ; Venugopalan, P. (2001) Efficient photocyclization of o-alkylbenzaldehydes in the solid state: direct observation of E-Xylylenols en route to benzocyclobutenols Journal Organic Chemistry, 66 (21). pp. 7013-7019. ISSN 0022-3263

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jo015718r

Related URL: http://dx.doi.org/10.1021/jo015718r

Abstract

The photocyclization to benzocyclobutenols of o-alkyl aromatic aldehydes that are predestined for γ-hydrogen abstraction is found to occur efficiently in the solid state; in contrast, solution-phase photolysis is known to afford a mixture of several products. It is shown that mesitaldehyde, which is a liquid, also undergoes efficient cyclization when subjected to photolysis as a solid inclusion complex. The marginal energy differences in the relative energies of the E-enols and the corresponding cyclobutenols in the case of cyano-substituted mesitaldehydes has permitted direct observation, for the first time, of the E-enols en route to benzocyclobutenols. The AM1 calculations suggest that the cyano-substitution causes intrinsic stabilization of the E-enols relative to the corresponding cyclobutenols, while the bromo groups do the opposite. The lack of observation of the red color in bromo-and formyl-substituted aldehydes is attributed to rapid cyclization of the E-enols to the their respective cyclobutenols even at low temperatures.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:60722
Deposited On:10 Sep 2011 11:37
Last Modified:10 Sep 2011 11:37

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