Azine Grignard reagents, reactions

The transition metal catalyzed carbon-carbon bond formation between organomagnesium reagents and aryl (vinyl) halides has been one of the pioneering entries into cross-coupling chemistry. The reaction has been widely utilized since than in azine chemistry,22 with the limitation that the functional group tolerance of Grignard reagents is only moderate. Here only some of the more recent developments will be mentioned. 

Unsymmetrically -substituted borazines can be prepared by the reaction of IV-substituted borazines or h-trihalogeno-N-substituted borazines and the appropriate amount of Grignard reagent (94). Borazines unsymmetrically substituted on nitrogen have been prepared by the reaction of Hthium borohydride and ammonium chloride and alkyl ammonium chlorides (105,106), and by Uthiation of B- trime thylb o r azine followed by reaction with alkyl halides (107). 

The synthesis of 1,2,4-triazines 3 by reaction of 1,2,4-triazin-3(2//)-ones 1334 or 1,2,4-tri-azin-5(2//)-ones 2335 with Grignard reagents in an addition/elimination sequence has also been reported. 

A special type of reduction is the addition of an HX compound such as water, alcohols, ammonia, hydrazine, Grignard reagents, hydrogen cyanide, or sulfur dioxide in aqueous methanol. The dihydro-1,2,4-triazines formed can be oxidized to afford the aromatic 1,2,4-tri-azines, hence these reactions are discussed in Sections 2.2.1.2. and 2.2.1.5.5. 

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