Alkenes intramolecular nonbonding interactions

Adsorption alters the structure of an alkene, and the subsequent hydrogen transfers are accompanied by further changes in the organic moiety. The transition state for adsorption undoubtedly has greater double bond character than the transition state for the formation of the alkyl intermediate, which implies that intramolecular nonbonding interactions will be greater in the latter. 

A number of intramolecular cycloadditions of alkene-tethered nitrile oxides, where the double bond forms part of a ring, have been used for the synthesis of fused carbocyclic structures (18,74,266-271). The cycloadditions afford the cis-fused bicyclic products, and this stereochemical outcome does not depend on the substituents on the alkene or on the carbon chain. When cyclic olefins were used, the configuration of the products found could be rationalized in terms of the transition states described in Scheme 6.49 (18,74,266-271). In the transition state leading to the cis-fused heterocycle, the dipole is more easily aligned with the dipolarophile if the nitrile oxide adds to the face of the cycloolefin in which the tethering chain resides. In the trans transition state, considerable nonbonded interactions and strain would have to be overcome in order to achieve good parallel alignment of the dipole and dipolarophile (74,266). 

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