Microwave assisted base dependent regioselective synthesis of partially reduced chromenes, isochromenes and
Pratik Yadav1, Surjeet Singh, Satya Narayan Sahu
1Department of Chemistry, University of Delhi, North Campus, Delhi, 110007, India. ramendrapratap@gmail.com.
Abstract:
We have reported a microwave assisted base directed regioselective synthesis of partially reduced chromenes, isochromenes and phenanthrenes. Functionalized 4-(piperidin-1-yl)-5,6-dihydro-2H-benzo[h]-chromen-2-one-3-carbonitriles have been used as precursors, which on reaction with functionalized acetophenones in the presence of KOH in DMF under microwave irradiation yield (Z)-2-(2-aryl-5,6-dihydro-4H-benzo[f]isochromen-4-ylidene)acetonitriles. The use of NaH in DMF provides 3-aryl-1-(piperidin-1-yl)-9,10-dihydro phenanthrene-2-carbonitriles in excellent yield regioselectively. The use of cyclohexanone as a nucleophile source yields (Z)-2-(3,4,7,8-tetrahydro-1H-naphtho[2,1-c]chromen-6(2H)-ylidene)acetonitriles. The structure and geometry of isochromene have been proved without any ambiguity by single crystal X-ray diffraction.
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