L,2-Dimethoxy-4-

Reaction of 2-aminoethanethiol hydrochloride with hydroxymethylfurazan 61 in 48% aqueous hydrobromic acid (reflux, 24 h) gave a salt that on treatment with an equimolar amount of 3,4-dimethoxy-l,2,5-thiadiazole 1,1-dioxide and another amine gave compound 62 (84USP4471122) (Scheme 30). 

The pH dependence of the regioselectivity for the nucleophilic photosubstitution of 3,4-dimethoxy-l-nitrobenzene by n-butylamine gives21 2-methoxy-5-nitro-Af-butylaniline as the major product at pH = 11 (equation 19). At pH = 12, the ratio of the major product to 2-methoxy-4-nitro-7V-butylaniline increases to 12 1 the increased selectivity is caused by hydroxide ion, which can either promote exciplex formation or act as a base catalyst in deprotonation steps following the cr-complex formation22. 

Reaction of the iron complex salt 602 with the arylamine 921 in the presence of air led directly to the tricarbonyl(ri -4b,8a-dihydro-9H-carbazole)iron complex (923) by a one-pot C-C and C-N bond formation. Demetalation of complex 923 and subsequent aromatization by catalytic dehydrogenation afforded 3,4-dimethoxy-l-heptyl-2-methylcarbazole (924), a protected carbazoquinocin C. Finally, ether cleavage of 924 with boron tribromide followed by oxidation in air provided carbazoquinocin C (274) (640) (Scheme 5.120). 

There are several examples of arylnitrenium ion additions to alkenes (Fig. 13.54). For example, Dalidowicz and Swenton trapped A-acetyl-A-(4-methoxyphenyl)-nitrenium ion 112 with 3,4-dimethoxy-l-propenylbenzene and isolated products resulting from addition of the alkene to the ortho position of the nitrenium ion, giving cation 113, followed by its cychzation onto N (yielding 114) or the acetyl carbonyl group (yielding 115). 

N-Methyldihydro-5a-paravallarine, 7, 8 3-Methyl-3-(3,4-dimethoxy-l-naphthyl)-phthalide, 270... 

Bei Iangerer Reaktionszeit entsteht 3,4-Dimethoxy-l-athyl-benzol (vgl. oben). 

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