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An Efficient De Novo Synthesis of Partially Reduced Phenanthrenes through C−C Insertion

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journal contribution
posted on 2007-09-14, 00:00 authored by Ramendra Pratap, Vishnu Ji Ram
An efficient and novel approach to the synthesis of highly congested 3-alkyl-, 4-alkyl-, 3-aryl-, 3,4-dialkyl-, 4-alkyl-3-aryl-, and 3,4-diaryl-9,10-dihydro-1-sec-aminophenanthrene-2-carbonitriles has been delineated through the base-catalyzed ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by carbanion derived in situ from various ketones in moderate to good yields. 9,10-Dihydrophenanthrenes with and without substituent in the bay region are efficiently and regioselectively synthesized by using propanal and acetyltrimethylsilane as a source of carbanion. Even the synthesis of bisphenanthrenes has been achieved by the ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by 2-acetylphenanthrene in moderate yield. Highly substituted 3-amino-1-sec-amino-5,6-dihydrophenanthrene-2,4-dicarbonitriles have also been prepared from the reaction of 2-oxobenzo[h]chromene and malononitrile.

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