Reaction With Hydrazine, Secondary, and Tertiary Amines

6 Reaction With Hydrazine, Secondary, and Tertiary Amines 

The reaction of hydrazine with chloroform and base to yield diazomethane was reported by Staudinger some sixty years ago but remained of limited utility. The application of 18-crown-6 mediated phase transfer catalysis to this reaction has made it a preparatively useful method. By this method, hydrazine hydrate can be conveniently converted to diazomethane in almost 50% yield (see Eq. 3.11) [16]. 

Secondary amines react readily with dichlorocarbene to yield secondary formamides in good yield [17, 18]. Apparently, the secondary amine coordinates with dichlorocarbene, and after proton transfer a dialkylaminodichloromethane is produced. The latter undergoes basic hydrolysis under phase transfer conditions which evidently stops before appreciable cleavage of the formamide occurs. The reaction is formulated in equation 3.12 and several examples are tabulated in Table 3.5. 

Tertiary amines are generally inert to dichlorocarbene under phase transfer catalytic conditions. In fact, tertiary amines have been utilized as catalysts in the dichloro-cyclopropanation reaction of olefins (see Sects. 1.8, 2.2) [19]. The inertness of tertiary amines is probably a function of its reluctance to transfer an alkyl group from cationic nitrogen to anionic carbon after the initial coordination step has occurred. 

One example of the reaction of dichlorocarbene with a tertiary amine under phase transfer conditions has been reported [20]. 5,7-Diphenyl-1,3-diazaadamantan-6-one is transformed into l,5-diphenyl-N,N-diformylbispidin-9-one in 23% yield. This unusual reaction may be rationalized as follows. Coordination of dichlorocarbene with a nitrogen lone pair yields a zwitterion (VI). Neighboring nitrogen assists fragmentation and the iminium zwitterion VII results. Protonation and hydrolysis of VII followed by dichlorocarbene reaction with the resulting secondary amine yields the bis-formamide VIII. The sequence is formulated in equation 3.13. 

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