Reactions of enamines with dehydroaromatic compounds
摘要:
Benzyne reacts with enamines through a combination of ene and 2 + 2 cycloadditions. One of the two possible ene reactions is greatly favored. The three-dimensional intermediate, 1,2-dehydro-o-carborane, 1 eschews the 2 + 2 reaction in favor of the ene reaction that is less favored in the benzyne reactions. This preference is rationalized in terms of the different steric demands of the two intermediates.
Hydroboration. 86. Convenient conversion of aldehydes and ketones into the corresponding alkenes via hydroboration of their enamines. A remarkably simple synthesis of either (Z)- or (E)-alkenes
作者:Bakthan Singaram、Milind V. Rangaishenvi、Herbert C. Brown、Christian T. Goralski、Dennis L. Hasha
DOI:10.1021/jo00004a038
日期:1991.2
Aldehydes and ketones are converted into the corresponding alkenes via hydroboration of their enamines. Hydroboration of aldehyde enamines by 9-borabicyclo[3.3.1]nonane (9-BBN), followed by methanolysis, affords the corresponding terminal alkenes in 75-90% yields. Unsaturated aldehyde enamines produce the corresponding dienes under these conditions. Enamines derived from substituted cyclic ketones and heterocyclic ketones are readily accommodated in this reaction to afford the corresponding alkenes in very good yields. The synthesis of pure (Z)- or (E)-alkenes is readily achieved from the same acyclic ketone enamine by modification of the hydroboration-elimination procedure: (A) hydroboration by 9-BBN followed by methanolysis or (B) hydroboration by borane methyl sulfide (BMS) followed by methanolysis and hydrogen peroxide oxidation. Mechanistic rationale is provided.
SINGARAM, BAKTHAN;RANGAISHENVI, MILIND V.;BROWN, HERBERT C.;GORALSKI, CHR+, J. ORG. CHEM., 56,(1991) N, C. 1543-1549
作者:SINGARAM, BAKTHAN、RANGAISHENVI, MILIND V.、BROWN, HERBERT C.、GORALSKI, CHR+