pi.-Facial selectivities in cycloadditions to norbornyl- and norbornenyl-fused p-benzoquinones

Mehta, Goverdhan and Padma, S and Pattabhi, Vasantha and Pramanik, Animesh and Chandrasekhar, Jayaraman (1990) pi.-Facial selectivities in cycloadditions to norbornyl- and norbornenyl-fused p-benzoquinones. In: Journal of the American Chemical Society, 112 (8). pp. 2942-2949.

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Abstract

The stereochemistry of the Diels-Alder cycloaddition of several dienes to the facially perturbed dienophiles 2,3-norbornenobenzoquinone (3) and 2,3-norbornanobenzoquinone (4) has been examined. Unambiguous structural proof for the adducts formed has been obtained from complementary 'H and I3C NMR spectral data and in two cases through X-ray crystal structure determination. While 1,3-~yclopentadiene1, ,3-~yclohexadienea, nd cyclooctatetraene exhibit preference for addition to 3 from the bottom side, the stereochemical outcome is reversed in their response to 4.1,3-DiphenyIisobenzofuran and 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadieenneg aged 3 from the top side with marked selectivity, which is further enhanced in their reaction with 4. The observed stereoselectivities seem to be essentially controlled by steric interactons at the transition state. Model calculations provide support for this interpretation.

Item Type:	Journal Article
Publication:	Journal of the American Chemical Society
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Organic Chemistry
Date Deposited:	27 Apr 2011 07:23
Last Modified:	27 Apr 2011 07:23
URI:	http://eprints.iisc.ac.in/id/eprint/34982

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