REACTIONS OF CARBENE INTERMEDIATES FROM THE REACTION OF TRIALKYL PHOSPHITES WITH DIALKYL BENZOYLPHOSPHONATES - INTRAMOLECULAR CYCLIZATIONS OF 2-SUBSTITUTED DIALKYL BENZOYLPHOSPHONATES
Dv. Griffiths et al., REACTIONS OF CARBENE INTERMEDIATES FROM THE REACTION OF TRIALKYL PHOSPHITES WITH DIALKYL BENZOYLPHOSPHONATES - INTRAMOLECULAR CYCLIZATIONS OF 2-SUBSTITUTED DIALKYL BENZOYLPHOSPHONATES, Journal of the Chemical Society. Perkin transactions. I, (6), 1996, pp. 555-561
The reaction of dialkyl benzoylphosphonates 1 with trialkyl phosphites
leads to the formation of carbene intermediates 3 via the anionic int
ermediates 2. The carbene intermediates 3 (R = 2-PhO, 2-PhOCH(2), and
2-PhS) have been generated by heating the corresponding 2-substituted
dialkyl benzoylphosphonates with trimethyl phosphite and their subsequ
ent reactions investigated. Reactions proceed either by intermolecular
trapping of the carbene intermediates by trimethyl phosphite to give
novel ylidic phosphonates 4, or by intramolecular routes involving car
bene insertion into the pi-system of the phenyl ring in the substituen
t, Studies using methyl-substituted derivatives have shown that the fo
rmation of the thioxanthenylphosphonate 15 (X = S, R' = R '' = Me) pro
ceeds via a spiro diene intermediate 14(X = S, R' = R '' = Me).