Ring Expansion Reactions of Cyclic .beta.-Keto Phosphonates

Synthesis of Polyfunctionalized Bicyclo[5.3.1]undecadiene Ring Systems Using a Two-Carbon Ring-Expansion of Cyclobutene Intermediates

“…Some examples of this have been reported previously, starting from β-oxo phosphonates, [15] β-oxo sulfonium ylides, [16] or β-oxo esters. [17] These transformations apparently involve an initial Michael-initiated ring-closure (MIRC) [18] reaction; the bridgehead electron-withdrawing group (e.g.…”

[2 + 2] Cycloaddition of cyclic vinyl phosphonates with ketenes †

“…13 C NMR δ 169.6 (6) (d, J CP = 6.8 Hz), 98.4 (d, J CP = 195.8), 65.9, 61.2, 61.1, 31.5 (d, J CP = 16.6 Hz), 30.9 (d, J CP = 11.3 Hz), 21.0 (d, J CP = 13.6 Hz), 16.4, 16.3, 15.4. MS m/z (relative intensity): 248 (M ϩ , 5), 233 (13), 219 (24), 191 (12), 163 (68), 145 (15), 111 (32), 83 (70), 81 (67), 65 (40), 29 (base peak), 127 (67).…”

“…We have reported, however, that phosphonates are capable of inducing fragmentation reactions in a tandem Michael-aldol-fragmentation reaction of β-keto phosphonates. 14, 15 As part of ongoing studies in our laboratories, we have been interested in the use of phosphonates in fragmentation reactions. We envisioned that bicyclic systems such as 2 might undergo fragmentation to afford [nϩ2] ring enlarged products [eqn.…”

Regiospecific Vinyl Phosphate/β-Keto Phosphonate Rearrangements Initiated by Halogen−Metal Exchange

“…This rearrangement has given access to phosphonates inaccessible or impossible to prepare by classical methods, including some derived from nonracemic ketones . The product phosphonates have proven useful as intermediates for synthesis of natural products and some analogues, as nonracemic ligands for transition metal catalysts and as substrates for further studies of the reactivity of β-keto phosphonates . At the same time, efforts to trap the intermediate anions have met with limited success and with unsymmetrical ketones a mixture of regioisomers may result from the rearrangement.…”