Sequential approach to the synthesis of ‘U and Z’ shaped polycyclic heteroarenes

Organic & Biomolecular Chemistry

 

Hardesh K. Maurya ,  Sanjay K Gautam ,  Ramendra Pratap , Vishnu K. Tandon ,  Abhinav Kumar ,  Vikas Bajpai ,  Brijesh Kumar and Vishnu Ji Ram

Org. Biomol. Chem., 2012, 10, 4977              

DOI: 10.1039/C2OB25173FThe synthesis of three new classes of heteroarenes, built through the sequential fusion of naphthalene, benzo/naphtho[b]oxepine and thiochromene rings with pyran and pyrimidine ring system to give ‘U and Z’ shapes of structural frame work is reported. The methodology is based on the synthesis of pyran fused intermediates, 1-methylthio-3-oxo-5,6-dihydro-3H-benzo[f]chromene-2-carbonitrile (3), 4-methylthio-2-oxo-5,6-dihydro-2H-benzo/naphtho[b]pyrano[2,3-d]oxepine-3-carbonitriles (10, 20) and 4-methylthio-2-oxo-2,5-dihydrothiochromeno[4,3-b]pyran-3-carbonitriles (15) from the reaction of 2-tetralone, benzo/ naphtho[b]oxepin-5-ones and thiochromen-4-ones with methyl 2-cyano-3,3-dimethylthioacrylate respectively. Further condensation of intermediates 3, 10, 20 and 15 with amidines led to the formation of tetracyclic ‘U’ shaped 4-amino-2-aryl-7,8-dihydro-5-oxo-5H-naphtho[2,1-b]pyrimido[4,5-d]pyrans (8) and ‘Z’ shaped 4-amino-2-aryl-5-oxo-12,13-dihydro-5H-benzo/naphtho[b]oxepino[5,4-b]pyrimido[4,5-d]pyrans (12, 22) and 4-amino-2-aryl-5-oxo-5,12-dihydrothiochromeno[4,3-b]pyrimido[4,5-d]pyrans (17). Compound 12f forms chain of dimers through N-H∙∙∙O interactions as indicated by the X-ray structure analysis and the quantum chemical calculations performed at the MP2 level indicates that this interaction energy is 10 kJ mol.-1