Dialkyl heteroaroylphosphonates based on thiophene, pyrrole or furan have been prepared and their reactions with trimethyl phosphite investigated. Deoxygenation of the carbonyl groups in these heteroaroylphosphonates occurs to give carbene intermediates, which then undergo further reaction. In the case of the furan-3-oylphosphonates and those systems containing a thiophene or pyrrole ring, the major reaction pathway involves intermolecular trapping of the carbene intermediates by the trimethyl phosphite, leading to the formation of ylidic phosphonates that can be readily converted into the corresponding 1,1-bisphosphonates. However, in some furan-2-oylphosphonates the carbenes generated undergo ring-opening to initially give acyclic alkynylphosphonates which may react further to give other novel phosphorus compounds. The effects of substituents on the extent to which intermolecular trapping of the initially formed carbene competes with intramolecular rearrangement has been investigated. The latter process appears to be suppressed by a substituent at the 5-position of the furan ring, the resulting ylidic phosphonates being a rare example of an efficient intermolecular trapping of a furan-2-yl carbene.

The compound dimethyl‐2‐iodobenzoylphosphonate is unusual in that it forms well‐ordered crystals that clearly show short iodine‐oxygen interactions in which both the iodine and the oxygen are in their normal oxidation states. These interactions were studied using a new hybrid quantum mechanical–molecular mechanical approach that employs a polarizable molecular mechanics component. The electric field at the molecular mechanics atoms was calculated from a distributed multipole expansion of the wave function; this induced dipoles on the molecular mechanics atoms. The electrostatic potential in a spherical shell around the induced dipoles was reproduced through induced charges on the atomic center and those bonded to it using an analytical (rather than numerical) procedure. The new atomic charges (induced charges plus permanent charges) were then able to interact with the quantum mechanical entity and polarize the wave function. The procedure was iterated to convergence. The calculations show that the iodine atom becomes more positive in the crystal environment (modeled by a chain of three molecules of dimethyl‐2‐iodobenzoylphosphonate). Thus, while the cooperative effects of the crystal environment may not be the only feature stabilizing this unusual interaction, they do play a significant role in reducing the otherwise unfavourable iodine–oxygen monopole–monopole interaction. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 478–482, 2000

The carbene intermediates 3 (Z = 2-vinyl and 2-allyl, R = Me) have been generated by heating the corresponding 2-substituted dialkyl benzoylphosphonates with trimethyl phosphite and their subsequent reactions investigated.Reactions proceed by both intermolecular trapping of the carbene intermediates by trimethyl phosphite to give novel ylidic phosphonates 4, and by intramolecular carbene insertion to give cyclic systems.For the 2-vinyl-substituted system cyclisation leads to a mixture of the two indenylphosphonate isomers 12 and 13, whereas for the 2-allyl systeminsertion into the π-system occurs to give a cyclopropyl system 21.

We have previously shown that substituted bcnzoylphosphonates (1; Ar ˭ X-Ph) react with trimethyl phosphite to give anionic intermediates which in the absence of electrophiles decompose to give carbene intermediates (3). The nature of the subsequent reaction products depends on the type and position of the substituents on the aromatic ring.ll1 When proton donors are present the initially formed anionic intermediates (2) give the quasi-phosphonium salts (4) which usually decompose to give the phohphonate-phosphates (5). although for the case of (1; Ar ˭ 4-MeOPh) formation of the phosphonates (6) was observed.

Dimethyl 2-(methylamino)benzoylphosphonate has been prepared by the thermal decomposition of dimethyl 2-(N-tert-butyl-N-methylamino) benzoylphosphonate formed by the action of triethylamine on 1-tert-butyl-3-(dimethoxyphosphinyl)-1-methyl-2,1- benzisoxazolinium hexafluorophosphate. The reactions of both benzoylphosphonates with trimethyl phosphite proceed via carbene intermediates 4 to initially give ylidic phosphonates 5, which for 5 (X = 2-MeNH) undergoes cyclisation and rearrangement to give the novel 2-oxophosphorindoline 11.