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DOI: 10.1055/sos-SD-010-00864

Gallagher, P. T.Science of Synthesis, (200110708.

The reduction of nitrobiaryls, e.g. 56, with triethyl phosphite and the subsequent cyclization of the electrophilic nitrenoid intermediate to carbazoles, e.g. 57, proceeds in good to excellent yields (Table 1).[‌74‌] A variety of substituents are tolerated and the isolation and purification is straightforward. It has been reported that increasing the number of methyl substituents reduces the yield of carbazoles in this reaction.[‌75‌] In the initial studies by Cadogan, alternative deoxygenation reagents (triphenylphosphine, phosphorus trichloride) were investigated, but triethyl phosphite was the reagent of choice.[‌74‌] The reduction of aromatic nitro compounds as a route to heterocycles has been reviewed.[‌76‌]

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