Functionalized acyclic alkenes amines

Other examples of reactions of [2 + 2] additions of electron-rich and electron-deficient olefins have been reported which are mechanistically similar to those described above. The reaction of p-toiyl vinyl sulphone with enamines gives trans-aminocyclobutyl p-tolyl sulphone (50). The cyclobutyl sulphones (50) are readily cleaved under hydrolytic conditions, presumably via zwitterionic intermediates to the acyclic (51). The reaction is a useful synthesis of a,a-dialkyl-y-sulphone aldehydes. Alkene phosphonates also function as the electron-deficient partner in reactions with enamines. Diethoxyphosphinylethylene reacts with the enamines to give the [2 + 2] adduct (52). The aminocyclobutylphosphonate (52) is stable, but the amine may be eliminated under rather vigorous basic conditions to give the cyclobutenyl-phosphonate (53). 

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