DECYANATION OF TERTIARY NITRILES BY ALKYLLITHIUM REAGENTS OBSERVED DURING THE SYNTHESIS OF IMIDAZOLES PENDANT TO A QUATERNARY CARBON CENTER

We have devised a five-step synthesis of the new chemical entities 7a-d from 5-methoxytetralone, 1, via unsaturated nitrile 3, the reductive alkylation products 4a-d, and ketones 5a-d and 6a-d. Structures 7a-d are distinguished by the presence of a 4-imidazolyl moiety pendant to a quaternary center of the 1, 2, 3, 4-tetra-hydronaphthalene nucleus. The tertiary nitriles 4a-d can produce either the desired ketones 5a-d, 10a, b, or 11 in reactions in benzene or diethyl ether, or the decyanation products 12a, b, d and 13a, in reactions in THF. Apparently fragmentation in 4-centered transition state 9b to the decyanation products is favored as the Lewis base strength of the solvent increases. Synthetically, it is preferable to use CH3MgBr in benzene in the conversion of 4a-d to 5a-d. © 1990, American Chemical Society. All rights reserved.