A (1,3) strain in cis- and trans-5, 6-dihydro-4, 6-dimethyl-4H, 8H-pyrido [3,2,1-de]phenanthridin-8-ones

Nagarajan, Kuppuswamy ; Shah, Rashmi K. ; Fuhrer, Hermann ; Puckett, Reginal T. ; Narasimhamurthy, Mathur R. ; Venkatesan, Kailasam (1978) A (1,3) strain in cis- and trans-5, 6-dihydro-4, 6-dimethyl-4H, 8H-pyrido [3,2,1-de]phenanthridin-8-ones Helvetica Chimica Acta, 61 (4). pp. 1246-1256. ISSN 0018-019X

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/hlca.19...

Related URL: http://dx.doi.org/10.1002/hlca.19780610407


The stereochemistry of trans- and cis-2, 4-dimethyl-tetrahydroquinolines, 6 and 7 were derived from 1H-NMR. studies. These were converted respectively into trans- and cis-5, 6-dihydro-4, 6-dimethyl-4H, 8H-pyrido [3, 2, 1-dephenanthridin-8-ones 18 and 20 by a Pschorr reaction on the anthranilamides 10 and 15. Bromophenanthridones 19 and 21 were similarly prepared from bromoanthranilamides 12 and 17. Detailed 1H-NMR. studies on 18 and 20 indicated axial disposition of the methyl groups at C(2) in both compounds in contrast to the situation in 6 and 7. This is presumably to avoid adverse CH3CO group interaction of the A (1, 3) type. The severity of this is gauged by the preference of 20 for a normally forbidding 1, 3-diaxial orientation of two methyl groups. X-ray crystallographic studies on 19 and 20 confirm the stereochemical assignments.

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