Henrietta Forintos

New evidence on the structure of the product from the reaction of cyclic 2,4,6-trialkylphenylphosphine oxides with dimethyl acetylenedicarboxylate (DMAD); formed by an inverse Wittig reaction type protocol

New evidence based on spectroscopy, quantum chemical calculations and reactivity suggest that the spirocyclic oxaphosphetes (5) formed by the [2+2] cycloaddition of the title P-heterocycles (4) and DMAD are intermediates to afford a stabilised phosphonium ylide (6) existing as two conformers (6A and B).

Synthesis of the Spiro Derivatives of 1,2-Oxaphosphetes by [2+2] Cycloaddition of Cyclic 1-(2,4,6-Triisopropylphenyl)phosphine Oxides with Dimethyl Acetylenedicarboxylate†

Abstract Members of a new heterocyclic family, 1,2-oxaphosphetes were prepared by the unexpected [2+2] cycloaddition of the PO group of 1-(2,4,6-triisopropylphenyl) P-heterocycles with the acetylene moiety of dimethyl acetylenedicarboxylate. The new oxaphosphetes are spiro derivatives of the starting heterocycles and exhibit a phosphorus atom with trigonal bipyramidal geometry. PM3 semiempirical calculations justified the novel reaction path and suggested a stepwise reaction mechanism.

Reactions of β-oxo-α,β-bis(alkoxycarbonyl)phosphonium ylides based on P-heterocycles

The title phosphonium ylides give an ylidene oxolactone under reductive conditions and are unreactive towards aldehydes, but are degraded by hydroxylamine to form the simpler acetic ester phosphonium ylides that do react with aldehydes in the normal manner.

Structure and stability of oxaphosphetes formed as intermediates in the reaction of tertiary phosphine oxides and acetylenic derivatives

Quantum chemical calculations showed that oxaphosphetes with an equatorial oxygen atom may be intermediates in the reaction of acetylenic derivatives and phosphine oxides with electron-releasing substituent(s) on the phosphorus atom.

Inverse Wittig reaction of oxaphosphetenes formed by the [2+2] cycloaddition of arylphosphine oxides and dimethyl acetylenedicarboxylate (DMAD)

The intermediate oxaphosphetenes 2 formed by the novel cycloaddition of the PO group of arylphosphine oxides 1 and the acetylene moiety of DMAD are stabilised by an inverse Wittig reaction to afford the corresponding stabilised phosphonium ylide 3.

On the cycloaddition of arylphosphine oxides with dimethyl acetylenedicarboxylate

Abstract The [2+2] cycloaddition reaction of dimethyl acetylenedicarboxylate (DMAD) and the PO moiety of cyclic P-(2,4,6-triisopropylphenyl) phosphine oxides giving an entry to oxaphosphetes is of general value and extended to cyclic and alicyclic phosphine oxides with different trialkylphenyl substituents on the phosphorus atom. The structures of the products obtained by the [2+2] cycloaddition have been studied by semiempirical quantum chemical calculations

Synthesis of 1‐Aryl‐1,2,3,4,5,6‐hexahydrophosphinine 1‐Oxides

Abstract Possibilities for the synthesis of 1‐(2,4,6‐triisopropylphenyl‐)1,2,3,4,5,6‐hexahydrophosphinine oxide (2) have been explored. The trivial method based on the hydrogenation of the corresponding dihydrophosphinine oxides (8a–e) was suitable only for the preparation of hexahydrophosphinine oxides containing a trimethylphenyl or methylphenyl group on the phosphorus atom (9a–c). The triisopropylphenyl product (2) was synthesized by the stepwise reduction of the double bonds of starting material 1. Hence, the ring contraction side reaction, observed during the catalytic hydrogenation, could be eliminated. The unusual reactivity was studied by quantum chemical calculations.

Generation and utilisation of P-cyclic α-methoxycarbonyl- methylenephosphoranes

Phosphonium salts 3 obtained by the quaternisation of 1-aryl-2,5-dihydro-1H-phospholes 2 with methyl bromoacetate are suitable precursors of the corresponding heterocyclic phosphoranes 5. They were generated in situ using DBU at ambient temperature. The phosphoranes (5) were used in Wittig reaction with benzaldehydes and in acylation with methyl (chloroformyl)formate to afford in the latter case, heterocyclic α,β-bis(methoxycarbonyl)-β-oxophosphoranes (7).

A Novel Reaction between the P=O Group of Cyclic 2,4,6-Trialkylphenylphosphine Oxides and Dimethyl Acetylenedicarboxylate (DMAD)

The reaction of cyclic P-aryl phosphine oxides with DMAD affords ylides/phosphoranes via oxaphosphetes.

Detection of the enantiomers of P-stereogenic pentacoordinated phosphorus compounds: 31P NMR of oxaphosphetes in optically active solvents

Abstract The enantiomers of spirocyclic oxaphosphetes possessing the sterically bulky 2,4,6-triisopropyl-phenyl group bound to the pentacoordinated phosphorus stereogenic centre could be distinguished in optically active amines as solvents.