Isoquinoline-bromine initiator

Figure 2.1 Relationship between rate of reaction, Rp, and initiator concentration [I], for isoquinoline-bromine complex in methyl methacrylate (J. W. Nicholson, unpublished results, 1977)...

Detailed analyses of each of these major classes of photopolymer sensitization will be presented below. A related process which is sensitive to visible light, which will not be discussed, is irradiation of charge transfer complexes, exemplified by the initiating complex between isoquinoline and bromine. See ref. 13. 

Codeine has also been prepared in 70% overall yield, again without purification of intermediate compounds, from dihydrothebainone (132) by the route (132) — (137) shown in Scheme 4. The initial product of the action of bromine and then alkali on dihydrothebainone is the 1,7-dibromo-derivative of dihydro-codeinone, which can be reduced to dihydrocodeinone (133). This may be converted into 7-bromodihydrocodeinone dimethyl ketal (136), which on treatment with potassium t-butoxide in DMSO at 120 °C is converted exclusively into thebaine, but at 60 °C the product is codeinone dimethyl ketal (137), which can be hydrolysed to codeinone (131).154 The process has obvious value in the possible synthesis of codeine via dihydrothebainone, for which a patent has been filed covering a process that proceeds from the reduced isoquinoline (138) 155 the conversion of A-formylnordihydrothebainone into dihydrothebainone by hydrolysis and reductive methylation and by ketalization, reduction, and hydrolysis has been reported.156... 

Introduction of halogen to the hetero-rings occurs under remarkably mild conditions in which halide addition to a salt initiates the sequence. Thus treatment of quinoline or isoquinoline hydrochlorides with bromine produces 3-bromoquinoIine and 4-bromoisoquinoIine, respectively, as illustrated below for the latter. ... 

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