Diels-Alder Reactions ofin situ generated N-benzoylindolo-2,3-quinodimethane with carbodienophiles
摘要:
The indolo-2,3-quinodimethane (5), generated from 2,3-bis(bromomethyl)indole (4), was trapped with unsymmetrical carbodienophiles or N,N'-p-phenylenedimaleimide to furnish the 1,2,3,4-tetrahydrocarbazoles (6 - 9). [4 + 2]-Cycloaddition of 5 with tetracyanoethylene gave rise to the tetracyanocarbazole (10) and a subsequent product 11 a or 11 b. The Diels-Alder reaction of 5 with divinyl sulfone was regiospecific within the detection limits of HPLC analysis. Similarly, the reaction of 5 with N,N'-p-phenylenedimaleimide yielded solely the stereoisomer 9.