One pot synthesis of polycyclic oxygen aromatics. Part III mechanism of formation

Kasturi, TR and Mandal, AB and Reddy, Amruta P and Prasad, Ganesha KB and Rajasekhar, B (1991) One pot synthesis of polycyclic oxygen aromatics. Part III mechanism of formation. In: Tetrahedron, 47 (28). pp. 5245-5258.

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Abstract

Reaction of 6-Image -butyl-1-bromomethyl-2-(2-tetrahydropyranyloxy)-naphthalene2c with tetrachlorocatechol (TCC) in acetone in presence of K2CO3 gave diastereomers 6c and 7c. A mechanism (Scheme-1) invoking the base induced cleavage of the pyranyl ether 2 to 1,2-naphthoquinone-1-methide 8 as the first step has been postulated. The cleavage of the pyranyl ether linkage in 2 to give dimers 4 and 5 of 1,2-naphthoquinone-1-methide has been demonstrated with different bases. 1,2-Naphthoquinone-1-methide 8, thus generated, undergoes Michael addition with TCC followed by elimination of chloride ions to give a diketone, which further undergoes aldolisation with acetone to give diastereomers 6 and 7. Michael reaction of 8, generated Image from pyranyl ethers 2a-c, with tetrabromocatechol (TBC) under similar-reaction conditions gave the expected monobromo compounds 6h, 6i, 6k, 7n, 7n and 7q. The last step in the proposed mechanism, Image ., aldolisation has also been demonstrated using different ketonic solvents. Thus, reaction of 2a-c with TCC/TBC in diethyl ketone/methyl ethyl ketone under similar reaction conditions gave the expected compounds 6 and 7.

Item Type:	Journal Article
Publication:	Tetrahedron
Publisher:	Elsevier science
Additional Information:	Copyright of this article belongs to Elsevier science.
Department/Centre:	Division of Chemical Sciences > Organic Chemistry
Date Deposited:	26 Nov 2010 06:35
Last Modified:	26 Nov 2010 06:35
URI:	http://eprints.iisc.ac.in/id/eprint/34017

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