Palladium-mediated reactions sulfones

In 1996, Fuchs and Jin (85), continuing to exploit the chemistry of vinyl sulfones, reported a stereospecific synthesis of the azabicyclic ring system of the cephalotaxine ring by means of palladium(0)-mediated aminospiro-cyclization of tertiary allylic sulfones, as shown in Scheme 53. Treatment of compounds 305 and 306 with either triethylamine or tetramethylguanidine (TMG) in the presence of Pd(Ph3P)4 produced the spiro azabicycles 307 and 308, respectively. The tertiary allylic sulfone 309, under identical reaction conditions, yielded 310, which contains the A/CVD ring system of cephalotaxine. 

Copper complexes have been used as reagents and as catalysts for the formation of carbon-carbon bonds. The most utilized reactions mediated by copper have been couplings of alkyl halides and sulfonates because copper complexes were unique for many years as reagents that would mediate the nucleophilic substitution of alkyl and aryl nucleophiles with alkyl halides. In recent years, work has been conducted to develop copper-catalyzed versions of cross couplings with aryl halides to address the issues of the cost of palladium catalysts. Although few examples of these processes currently rival those catalyzed by palladium complexes, they do illustrate the potential of copper complexes to catalyst these types of cross-coupling processes. 

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