Phosphorane, methylene-, derivatives

A further example of the diazaphosphole synthesis by [3 + 2] cycloaddition is given by the reaction of a phosphoranediyl diazomethane (26) (R = NPr j) with P-chloro-bis(trimethylsilyl)-phosphaethene. The adduct loses trimethylchlorosilane and yields a 3-phosphoranediyl-l,2,4-diazaphosphole (or 3-phosphonio-l,2,4-diazaphospholide) (27). The analogous addition to the trimethylsilyl substituted P-chloro-bis(methylene)phosphorane (28) yields a 4-methylene derivative (29) of this diazaphosphole (molecular structure in Table 1). It provides the only fully characterized example of this type up to 1995. Methyl triflate methylates the compound at N-1 and gives a phosphonio methylene diazaphosphole cation (30). 

Removal of the photolabile acid protecting group afforded the unstable sodium salt (128). Various esters (131) of (128) have been prepared 107) using the phosphorane (130) derived from the 4-allylazetidinone (129) in this case oxidation of the terminal methylene grouping by ozonolysis provided the aldehyde for the intramolecular Wittig reaction. Both the p-nitrobenzyl ester (108) and acetonyl ester 109,110) of (131) have been used in this way to prepare (128). 

Methylene phosphorane derivatives, Scheme 23, react with Se to give the corresponding selenoketones.18,24,223 225... 

The 2-vinyl derivatives 256-258 were obtained by standard Wittig methylenation of the corresponding aldehydes <1996GCC888, 1997CCC1468> (Equation 5) with methylene(triphenyl)phosphorane in 54-78% yield after chromatographic purification. 

On the other hand, optically active 43 and 44 were synthesized as follows.401 Treatment of 2,3,4-tri-0-benzyl-l,5-di-0-tosyl-D-arabinitol (277) with three equimolar proportions of methylenetriphenylphos-phorane gave the cyclic phosphorane (278), which was stereoselectively converted into the cyanohydrin (279) by way of the corresponding C-methylene and inosose derivatives. Compound 279 was converted into 43 and 44 by way of the corresponding carboxylic acid (280), and unsaturated nitrile (281), respectively. Compound 39 was derived from the inosose (282), obtained from quebrachitol, through a 21-step conversion.402 Introduction of a hydroxymethyl group into 282 was accom-... 

Bis(imino)phosphoranes, R-P(=NR )2 of various types, methylene-iminophosphoranes, R-P(=CR2)(=NR0 as well as numerous iminooxo, iminothio, and iminoseleno derivatives, RP(Q)(=NR0 (Q = O, S, Se), are known and have been reviewed. 

The [(aryldiazenyl)methylene](tripheny])phosphoranes 1 afford in good yields the quina-zolin-4(3//)-one derivatives 2 via a facile thermally promoted rearrangement, withN=N bond cleavage and elimination of triphenylphosphane. ... 

We have proceeded to apply the ring fragmentation approach to the generation of yet another type of previously unknown 3-coordinate phosphoryl derivative, where the methylene(oxo)phosphorane has an alkoxy substituent on phosphorus. Such structures (26-29) can be considered as anhydrides of monoalkyl alkylphosphonates. The precursors for these new species have the structures 22-25 (isomer mixtures) they are known compounds (72) from our previous work and are synthesized by the cycloaddition reaction of dihydrophosphinines with dimethyl acetylenedicarboxylate, as used in Scheme 4. 

Highly electrophilic P-lactams such as 36 and 38 have been shown to react with stabilised phosphoranes to yield azetidin-2-methylenes 37 and 39 [30] respectively (Scheme 13). However this reaction did not occur with less reactive P-lactams e.g. monocyclic P-lactams or cephem derivatives. The olefins 37 and 39 can be used as protected P-lactams they are much more stable to basic and nucleophilic conditions, and they readily regenerate P-lactams by ozonolysis [30]. The de-esterification of 37 and 39 by conventional methods gave the acids (R = H) which are very weak antibacterial agents or P-lactamase inhibitors. 

At least three names are available for the compound H3P=CH2. These are phosphine methylene, methylene phosphonium ylid and phosphonium methylide moreover, the compound can be classed as a phosphorane The compound PhjP Rj may be called triphenylphosphonium methylide, tri-phenylphosphonium methanide or triphenyl-methylenephosphorane. The pyridine analogue, C5H5P, has been known variously as phosphobenzene, phosphabenzene, phosphorin, and most recently, phosphinine. The term phosphane for (1) in Table 1.4 and its derivatives is the most recent and the most systematic, but it is difficult to see how the more widespread and firmly rooted term phosphine will ever be replaced. In addition, adoption of the term phosphane would put it in line with such little-used terms as carborane for CH4, nitrane for NH3 and oxane for HjO. 

While some of the parent carbophosphenes (6.2) probably exist as spectroscopic species, only their derivatives have in some cases been characterised. Most numerous of known species are those of type (6.2a) (methylene phosphines, 6.2e) (methylene phosphoranes). Mixed varieties such as (6.2g) have only recently been reported [19],... 

Another [2+2] cycloaddition reaction of carbon suboxide is encountered in the double Wittig reaction with the methylene phosphorane 48, which affords the 1,2,3,4-pentatetraene derivative 49 in 46 % yield . ... 

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