Reduction of N-Nitrosodiphenylamine to unsym-Diphenylhydrazine by Lithium Aluminum Hydride¹

Solvent Effects on the Reactivity and Free Spin Distribution of 2,2-Diphenyl-1-picrylhydrazyl Radicals1

“…The hfcc of the nitroxide in ethyl acetate (3) was not measured by Knauer and Napier 17a but was estimated from data for di-tert-butyl nitroxide, see footnote f to Table IV [ 15 N2]-1,1-Diphenylhydrazine. 23,24 N-[ 15 N]-nitrosodiphenylamine (2.1 g; 10.5 mmol) was reduced with 1.5 equiv of LiAlH4, using the method of inverse addition, 25 in anhydrous ether for 1 h at 0-5 °C. After decomposition of the reduced intermediate (EtOAc 20 mL, wet ether 20 mL, 20% sodium potassium tartrate 70 mL), the organic layer was separated and then combined with ether extracts of the aqueous phase (3 × 50 mL), dried (Na 2SO4), and concentrated to 100 mL under vacuum.…”

An Organic Chemist’s Guide to N-Nitrosamines: Their Structure, Reactivity, and Role as Contaminants

“…71 Hydride reduction using LAH generally provides fair to good yields of 1,1-dialkyl or 1,1-alkylaryl 27, 50,72−74 but diarylnitrosamines are easily over-reduced to give the parent amine and ammonia 73 unless the reaction conditions are carefully controlled. 75 Reduction of 1 can be effected with sodium metal in either absolute ethanol or ethanol in liquid ammonia, but the yield is lower than with LAH for many substrates. 72 TiCl 4 with magnesium powder in dichloromethane/diethyl ether solution forms a reducing Ti(II) reagent that reduces a variety of nitrosamines to hydrazines in excellent yields (>90% typically), though the reagent must be made fresh for each reaction.…”

“…Catalytic hydrogenation was of interest for industrial purposes, and Pd/C, Pt/C, and Rh/C all yield the corresponding hydrazines, although the yield of 27 is strongly dependent on reaction conditions and the identity of 1 . , The yield of 27 by catalytic hydrogenation is improved by the inclusion of a salt (e.g., NH 4 OAc, CaCl 2 ) in the reaction mixture . Hydride reduction using LAH generally provides fair to good yields of 1,1-dialkyl or 1,1-alkylaryl 27 , ,− but diarylnitrosamines are easily over-reduced to give the parent amine and ammonia unless the reaction conditions are carefully controlled . Reduction of 1 can be effected with sodium metal in either absolute ethanol or ethanol in liquid ammonia, but the yield is lower than with LAH for many substrates .…”

Indole synthesis – something old, something new

“…Alternatively, N-substituted arylhydrazines can be prepared by reduction of the N-nitroso derivative, although the toxicity associated with nitrosamines renders this far from ideal. This reduction can be effected with zinc dust in acetic acid 12 or lithium aluminium hydride; 13 sodium dithionite provides a milder alternative, 14 and has been used on pilot plant scale in the synthesis of the 5HT 2C receptor agonist 7 (Scheme 8). 15 Hydroamination of alkynes represents another approach to the required enehydrazine intermediates.…”