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First General Approach to Cyclohex-3-ene-1,1-bis(phosphonates) by Diels−Alder Cycloaddition of Tetraethyl Vinylidenebis(phosphonate) to 1,3-Dienes
journal contribution
posted on 2003-01-07, 00:00 authored by Renzo Ruzziconi, Giacomo Ricci, Antimo Gioiello, Hélène Couthon-Gourvès, Jean-Philippe GourvèsTetraethyl vinylidenebis(phosphonate) (VBP) reacts smoothly with substituted 1,3-dienes at 90−110 °C without solvent to give the corresponding cyclohex-3-ene-1,1-bis(phosphonates) in good yields
(60−85%). With nonsymmetrically substituted dienes, mixtures of regioisomers are obtained, the
regioisomeric ratio being exclusively controlled by electronic effects. Danishefsky's diene allows
tetraethyl 4-oxocyclohex-2-ene-1,1-bis(phosphonate) to be obtained in an 81% overall yield after
the acid-catalyzed hydrolysis of the Diels−Alder cycloadduct. With 2,3-dimethoxy-1,3-butadiene, a
mixture of regioisomeric dimethoxycyclohexene-1,1-bis(phosphonates) is formed by the VBP-catalyzed isomerization of the normal Diels−Alder cycloadduct. The mixture converges into
tetraethyl 3,4-dimethoxycyclohex-2-ene-1,1-bis(phosphonate) at prolonged reaction times.