Carbon-nitrogen double bonds dehydrogenation

Dehydrogenations, which involve the elimination of hydrogen Ifom organic molecules, lead to compounds containing double bonds, multiple bonds, or aromatic rings. For practical reasons, only the formation of carbon-carbon double bonds, of carbon-nitrogen double bonds in cyclic amines, and of aromatic rings (both carbocyclic and heterocyclic) will be discussed in this chapter. The conversion of alcohols into aldehydes and ketones and of amines into imines and nitriles will be discussed in the chapter Oxidations (Chapter 3). 

Double bonds between carbon and nitrogen in secondary and tertiary cyclic amines are formed on treatment with mercuric acetate [401, 402, 1091], silver oxide [375], or tert-butyl hypochlorite [707]. tert-Butyl hypochlorite converts methyl pyrrolidine-2-carboxylate into methyl 1-pyrrol ine-2-carboxylate in 71% yield [707], and mercuric acetate transforms 2-terr-butylpiperidine into 2-tm-butyl-l-piperideine in 75% yield [1091]. Tertiary cyclic amines are dehydrogenated by mercuric acetate via quaternary salts [401,402]. l-Methyl-2-ethylpiperidine yields ultimately 1-methyl-2-ethyl-2-piperideine [402] and quinolizidine A -dehydroquin-olizidine [401] (equation 34). 

---