Formation of carbon-nitrogen bonds via organomagnesium compounds

Formation of Carbon-Nitrogen Bonds via Organomagnesium Compounds 

Reactions of organomagnesium compounds with A -halogenoamines give variable proportions of halogen compounds and amines (see also Chapter 14)  

Once again, yields are somewhat unpredictable, but in many cases Grignard reagents give higher yields than the corresponding organolithium compounds. Some representative examples are shown in Table 11.1, and a procedure follows. 

A solution of cis, fru .s-2,3-diphenylcyclopropylmagnesium bromide (70 ml, 6.1 mmol) is prepared from l-bromo-cA,/rans-2,3-diphenylcyclopropane (2.46 g, 9.0 mmol) and magnesium (2.46 g, 10.0 mmol) in diethyl ether (80 ml) and added at -10° to a suspension of /V.N-dimethyl-O-mesitylsulfonylhydroxylamine (1.50 g, 6.1 mmol) in THF (20 ml). The mixture is allowed to warm to 25° and stirred for 15 h. Hydrochloric acid (2 m, 20 mi) is added, and the aqueous layer is separated, extracted twice with ether, and basified (2 M NaOH, 20 ml). The resulting alkaline solution is extracted three times with ether. The extract is dried (MgS04), the solvent is evaporated, and the residue (880 mg, 52%) is recrystallized from ether/pentane to give 1-dimethylamino-cis,trans-2,3-diphenylcyclopropane (790 mg, 47%), m.p. 66-68°. 

Reactions of organomagnesium compounds with nitroso or nitro compounds are often complicated, and not useful in synthesis, or only represented by isolated examples. One exception to this generalization involves conjugate addition to a,(3-unsaturated and aromatic nitro compounds (see Section 4.2), and two others lead to the formation of carbon-nitrogen bonds. 

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