Isoquinolyl radicals

In the absence of methoxide ion substitution takes place at a slower rate by an S jAr route. Formerly, the presence of methoxide ion in substitution reactions involving thiolate ions in methanol was avoided studiously in order to prevent a competing substitution by the methoxide ion. Although methoxide ion is required for the radical chain process to occur, only traces of substitution product containing the methoxy group are present, demonstrating that benzenethiolate ion is superior to methoxide ion in trapping the intermediate 4-isoquinolyl radical,116 Scheme 12. 

Initial reports on quinolyl and isoquinolyl radicals were first published in the 1970s (75JA1548, 73JA6863, 72JOC3199), but their use in the synthesis of heterocycles was first reported by Comins (94TL5331), where the synthesis of (S)-camptothecin 206 is described. The radical step takes place in the construction of the C ring (Scheme 54). 

Similar A-fluoro perfluoroheterocyclic sulfonamides of the type HetF(NF-S02R) have been synthesized, where HetF represents an aromatic perfluoroheterocyclic radical of valency n from naphthyridinyl, quinolyl and isoquinolyl.127... 

Bromoisoquinoline did not react with MeS ions in liquid ammonia, but 80% yield of the substitution product 4-isoquinolyl methyl sulphide was formed in the presence of amide ions. Isoquinoline and many other nitrogen-containing heteroaromatic compounds are known to react with amide ions to give anionic adducts 242289, which have been proposed to initiate the S l reaction by an ET to the substrate, which leads to the hetaryl radical. The radical couples only with MeS" ions 29°. 

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