Using NBS as a Mild Bromination Reagent for Polyalkoxyaromatic Systems

REFERENCES

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• Chenard , B. L. , Dolson , M. G. , Sercel , A. D. and Swenton , J. S. 1984 . J. Org. Chem. , 49 : 318 A derivative of 2a with an additional double bond (6-bromo-1,2-dihydro-5,8-dimethoxynaphthalene) was transformed into an anthracycline precursor by didehydrobenzene(benzyne) chemistry, see Khanapure, S. and Biehl, E.R. Synthesis, 1991, 33. We have prepared benzyne intermediates from a number of 1,2-dibromides including 2b and 3b by using lithium amalgam(J.L. Bloomer and Michael F. Parker, unpublished), but until the appearance of Biehl's LDA method we had limited success in preparing benzynes from the monobromo series. A combination of selective monobromination and benzyne formation via LDA now appears to hold much promise for the construction of linear polycyclic arrays via intermediates 1a-6a.
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• Tanoue , Y. , Terada , A. , Torisu , K. and Taniguchi , H. 1989 . Bull. Chem. Soc. Jpn. , 62 : 1211 The reported procedure yielded monobromide (44%), dibromide(17%) and unreacted starting material(3%), which have to be separated chromatographically. Our procedure gave monobromide in an improved yield(60%). We prepared 4 from naphthazarin using the ``reductive methylation'' procedure of Kraus(see reference 4).
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