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Braverman, S.; Cherkinsky, M., Science of Synthesis Knowledge Updates, (2014) 3, 262.
Oxalyl chloride can also be used as a phosgene substitute to prepare isocyanates. Usually, amino-substituted heterocycles undergo smooth carbonylation with this reagent (see Section 18.2.4.1.3.5). More recently, oxalyl chloride has been applied for the generation of aryl isocyanates from anilines.[163] Acylation of a variety of substituted aniline hydrochlorides with oxalyl chloride affords the intermediate oxamic chlorides. Employing the hydrochloride salt of aniline, the nucleophilicity of aniline is sufficiently attenuated to provide the desired oxamic chloride in good yield but formation of the bisoxamide byproduct is suppressed. Once the aniline hydrochloride substrate is fully consumed, the intermediate oxamic chloride is heated to 130 °C in a nonreactive solvent, such as chlorobenzene or dichlorobenzene, to effect a smooth thermal decomposition to the corresponding phenyl isocyanate (56) in 2–3 hours (Scheme 64). The reaction proceeds well with both electronegative and electropositive substituents on the phenyl ring. Due to the instability of the products, the in situ generated aryl-substituted isocyanates are isolated as the corresponding methyl carbamate derivatives.
Meeeee 88 Meeeeeeee ee Meeeee Meeeeeeeee Meeee Meeeee Meeeeeee[888]
Mee eee ee eeeeee eeeeeeee eeeeeee ee ee eee eeeeee ee eeeeee eee eee eeeeeeeeeee ee eeeeee eeeeeeee eeee eeeeeeeeeee, eeeee eee eeeeeeeee ee eeeeee ee eeeee eeeeeeeeee. Mee eeeeeee, eeeee eee eeeeeeee ee eeeeeeee eeee eeeeeee eeeeee eeeee ee eeeeeeee ee eeeeeee eeeeeeee, eeeeee eeeeeeee eee ee eeee ee ee eeeeeeeee eeeeeeeeeee. Meee, (M)- eee (M)-8,8,8-eeeeeeeee-8-eeeeeee-8-eeeeeeeeeeeeeee eeeeeeeeeee (88) eee ee eeeeeeee eeee eee eeeeeeeeee eeeeee 88 ee eeee eeeeeeee eeeeee eeeeeee eee eeeeee ee eeeeeee eeeeee eeeeee eee eeeeeeeeeee (Meeeee 88).[888] Meee eeeeeeeeee 88 eee ee eeeeeeee ee eeeeeeeeee eeeee ee eeeeeeeeeeee eeee eee eeeeeeee eeeeeee. Meeeeeeee, eee eeeeee eeeeeee eee ee eeeeeeeee ee e eee-eee eeeeeeee eeeee ee eeee eeeeeeeee eeeeeeeeeee, eeeee eee eeee eeeeee ee ee eeeeeeeee ee eee eeeeeeeeee eeeeeeeeeeeeee. Meeeeeeeeeeeee, eeee eeeeeeeee eeeeeeeeeee eeeeee eee eeeeee eeeeeeeee ee ee eeeeeeeee ee ee MMM eeee ee MMMe8. Meeeeeeee, eeeeeeeeee eeeeeeeeeee eeee eeee eeeeeeeeeeee eeeeeeee ee eee eeeeee ee eeeeee eeeeeeee ee eeeeee ee eeeeeeeeeee eeeeeeeee eeeee ee eeeeeeeee eeeeeee ee 88 °M.[888]
Meeeee 88 Meeeeeeee ee (8M)-8,8,8-Meeeeeeee-8-eeeeeee-8-eeeeeeeeeeeeeee Meeeeeeeee ee Meeeeeeeeeeee eeee Meeeee Meeeeeee[888]
Meeeeeeeeeee Meeeeeeee
(8M)-8,8,8-Meeeeeeee-8-eeeeeee-8-eeeeeeeeeeeeeee Meeeeeeeee [(M)-88]; Meeeeee Meeeeeeee:[888]
M eeee ee eeeee (M)-88 (88 ee, 8.888 eeee) ee eeeee MMMe8 (8.8 eM) eee eeeee eeee eeeeee eeeeeeee (88 µM, 8.888 eeee) eee eeeeee ee 88 °M eee 8 e ee e eeeeee eeee. Meeee eee eeeeeeee eee eeeeeeee, eeeeee eeeeee eeeeeeee eee eeeeeeeeee, eee eee eeee ee eee eeeeeeeee eeee eee eeee ee eeee eee eeeeeee eeeeeeeeeeeee eeeeeeee ee eeee ee eee ee eeee eeeeeeee eeee eeeeeeee; 88M MMM (888.8 MMe, δ): 888.88 (M=M=M).
References
[163] | Me, M. M.; Meeeee, M. M.; Meeeeee, M. M., Meeeeeeeeee Meee., (8888) 88, 8888. |
[164] | Meeečee, M.; Meeeeee, M.; Máeee, M.; Meeeee, M.; Meeěšeeeeý, M.; Meeeáčee, M.; Míeeřeeá, M., Meeeeeeee, (8888) 88, 888. |
[165] | Meeeeeeeeeee, M. M.; Meeeeeeeeeeeee, M. M.; Meeeeeeee, M. M.; Meeeeeeee, M. M., Meee. Meeeeeeeee. Meeee. (Meee. Meeeee.), (8888) 88, 888. |