Phosphorus carbon halides

Organophosphorus compounds. Phosphorus-carbon bond fonnation takes place by the reaction of various phosphorus compounds containing a P—H bond with halides or tritlates. Alkylaryl- or alkenylalkylphosphinates are prepared from alkylphosphinate[638]. The optically active isopropyl alkenyl-methylphosphinate 778 is prepared from isopropyl methylphosphinate with retention[639]. The monoaryl and symmetrical and asymmetric diarylphosphi-nates 780, 781, and 782 are prepared by the reaction of the unstable methyl phosphinate 779 with different amounts of aryl iodides. Tnmethyl orthoformate is added to stabilize the methyl phosphinate[640]. 

In contrast to the inertness of carbon halides, the halides of silicon and phosphorus are extremely reactive with water, to the extent that they must be protected from atmospheric moisture. A clue to the reactivity of these halides is provided hy the somewhat Similar reactivity of acid halides which readily react with water... 

When this type of reaction was applied to the preparation of the ester 2, phosphorus trichloride was used as the phosphorus (III) halide. Treatment of this with one mole equivalent of 3,3-dimethoxyprop-l-ene yields mainly the enol ether 4, with smaller amounts of the isomeric a-chloroallyl methyl ether 5. This mixture is not very stable and has to be treated with trimethyl phosphite rapidly, in order to provide 2 in good yield, as shown in Scheme 1. The significance of this sequence is that it reveals that since 2 is the only product, the reactions leading to 2 via 4 must proceed by two allylic inversions, whilst those via 5 involve direct substitution twice at the original acetal carbon. 

The fundamental chemistry and compounds reported prior to 1984 are summarized in CCC (1987). The development and expansion of coordination chemistry provided many possibilities and opportunities for the selection of ligands. Many combinations of coordinated atoms have been reported including halogen, chalcogen, nitrogen, phosphorus, carbon, and hydrogen. Initially, classical halides and their derivatives are described, followed successively by less electronegative atoms. 

Miscellaneous Methods of Preparing Phosphines. Palladium-catalysed formation of phosphorus-carbon bonds continues to be developed as a useful route to organophosphines. The reactions of primary or secondary phosphines with aryl- or vinyl-halides in the presence of a palladium catalyst, usually palladium acetate or a zerovalent palladium-phosphine complex, have been used in the synthesis of steroidal phosphines, e.g., (128), the cationic diphosphine system... 

In addition to the above-mentioned aluminum halides (Section 6.5.3.1), triorganoaluminum reagents are also able to initiate cyclooligomerization processes of the phosphaalkyne 9 a. In these reactions, aluminum is incorporated directly into the cage system. The element combination phosphorus, carbon, aluminum in a polycyclic system was previously unknown. The product palette is highly influenced by the choice of the solvent and the substituents at the metal center. 

Although those Michaelis-Arbuzov reactions which involve acyl halides and phospho-rus(III) esters are yet a further route to phosphorus-carbon bond formation and will be discussed later in Section VI, the use of halogenated acyl halides has led to some unusual results which, conveniently, can be summarized here. The products obtained from reactions between trialkyl phosphites and perfluoroacyl chlorides contain both phosphonate and phosphate moieties and are structurally dependent on reaction temperature. The initial product (Scheme 4) is thought to be the ylide 66. In an ethereal solvent at low temperature, decomposition of the ylide yields [l-(dialkoxyphosphinoyl)oxy-l/f-perfluo-roalkyl]phosphonates (67) exclusively, but at -20 °C and above, and in the absence of a solvent, the products consist of (Z)-[l-(dialkoxyphosphinoyl)oxyperfluoroalkene]phos-phonates (68) . The treatment of the compounds 67 with Ida yields 68, and the action of BuLi-CuI on 68 results in loss of the phosphate moiety to give the esters 69 The structural isomers 70 of the compounds 68 have been obtained as illustrated in equation... 

Of course, the gas-phase thermochemistry of ions is not solely restricted to the measurement of the quantities described above a wide range of other ion affinities have been measured, including methyl cation affinities, hydride affinities and halide affinities . Further, such measurements can often be related to unknown neutral thermochemistry via the appropriate thermochemistry cycle. For example, the phosphorus-carbon double bond strength (the sum of the a and n bond contributions) in HP=CH2 was recently estimated via mass spectrometric measurements to be 101 7 kcaF (ref. 43). 

---