Dehydrogenation copper bromide

In addition to this, other reports indieate that eopper has exhibited eatalytic behaviour in the formation of a-ketoamides by cross-dehydrogenative eoup-ling. Copper bromide was used catalytieally in the synthesis of bioaetive compounds using this approach (Scheme 17.21). ... 

Scheme 17.21 Synthesis of epoxide hydrolase inhibitor via copper bromide catalysed cross dehydrogenative coupling of aldehydes and...

Copper(II) bromide is another reagent that has been used successfully for the dehydrogenation of ketones and amides (equation 21). This procedure, which presumably proceeds via the a-bromo compounds, (c/. Section 2.2.2) was found to have particular advantages over a number of alternative methods for the dehydrogenation of some dihydrouracils. ... 

The ring synthesis of the tetrahydro-1,3-azoles is simply the formation of N,N-, N,0-or A, S-analogues of aldehyde cyclic acetals the ring synthesis of the 4,5-dihydro-heterocycles requires an acid oxidation level in place of aldehyde. A good route to the aromatic systems is therefore the dehydrogenation of these reduced and partially reduced systems. Nickel peroxide, " manganese(IV) oxide, copper(II) bromide/ base, and bromotrichloromethane/diazabicycloundecane have been used. The example shown uses cysteine methyl ester with a chiral aldehyde to form the tetrahydrothiazole. 

Alternatively, McMurray coupling of a,a -thiobis(aryl)ketones leads to 2,5-dihydroihiophenes, using comparable conditions, but at a higher temperature [105, 106]. The 2,5-dihydrothiophenes can easily be dehydrogenated to the 3,4-diarylthiophenes, with DDQ [105] or copper(II) bromide [107]. 

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