J. Campbell, T. D. Greenwood, S. B. Hendi
Aug 1, 1996
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Journal
Heterocyclic Communications
Abstract
2-(2-Lithiophenyl)ethyl chloride 4 condenses with appropriately substituted imines 5a-c (Ri = H, R2 = aryl, R3 = aryl, benzenesulfonyl) to give the corresponding 1,2disubstituted 1,2,3,4-tetrahydroisoquinolines 6. Hindered imines 5f-g (R-|, R2 = aryl) or N-alkyl substituted imines 5e-f fail to react, while those bearing α-hydrogens react as acids with 4, thus precluding formation of 6. Treatment of 4 with phenanthridine affords 10,11-dihydrotribenzo[a,c,h]15bH-quinolizine 6e in a convenient one-step synthesis. 2-Substituted-3,4-dihydro-1 (2H)-isoquinolinones 8 are obtained in good yields from the reaction of 4 with alkyl and aryl isocyanates 7. Introduction In connection with a search for convenient, new methods for the synthesis of isoquinolines and isoquinolinones, we were drawn to earlier reports of the preparation of indolines 1 (1) and phthalimidines 3 (2) via reactions of 2-lithiobenzyl chloride 2 with imines and isocyanates, respectively. The success of these reactions prompted us to investigate the feasibility of developing possible general syntheses of isoquinolines 6 and isoquinolinones 8 by similar reactions utilizing 2-(2-lithiophenyl)ethyl chloride 4. We now report on the scope and limitations of this synthetic method. ~ ι ArCH=NAr r ^ V ^ C I ArNCO i; , N ~ A r 1 I I N A r v Li Ar Ο 1