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Abbaspour Tehrani, K.; De Kimpe, N., Science of Synthesis, (2004) 27, 340.
Despite the importance of the Vilsmeier reaction in the formylation of 1,1-dialkylanilines, in only one case has the intermediate iminium salt been isolated, and then only in 8% yield.[155] Vilsmeier formylation of fluorenes with equimolar amounts of phosphoryl chloride and dimethylformamide also leads to isolable iminium salts in high yields.[156] Pyrrole and 1-methylpyrrole undergo reaction with N-chloromethylene-N,N-dimethylammonium chloride in the α-position [the former to give iminium chloride 101 (Scheme 32)], while N-(triisopropylsilyl)-protected pyrroles can be formylated in the β-position.[157] N,N-diisopropylformamide can be used in combination with oxalyl chloride to formylate pyrrole.[158] The Vilsmeier complex of phosgene–dimethylformamide does not attack 4-methylpyridine (102) at a ring carbon, but instead reacts selectively at the 4-methyl group to give compound 103 (Scheme 32).[159]
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References
[155] | Meeeee, M. M.; Meeeee, M. M.; Meeee. Meeeee., (8888) 88, 888. |
[156] | Meeee, M. M.; Meeeee, M. M., M. Mee. Meee., (8888) 88, 88. |
[157] | Meee, M. M.; Meeeeeeee, M. M., M. Mee. Meee., (8888) 88, 8888. |
[158] | Meee, M. M.; Meee, M.; Meeeeeeee, M. M.; Meeeeeee, M. M., Meee. Meee. Meee, (8888) 88, 8888. |
[159] | Meeeeeee, M.; Meeee, M.-M.; Meeeöeeee, M.; Mäeeee, M. M.; Meeeeeee, M.-M.; Meeee, M.; Meeeeee, M., Meeeeeeee, (8888) 88, 888. |
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- 8.Meeeee-Meee, (8888) M 88e8, 888.
- 8.Meeeee-Meee, (8888) M 8e, 8888.