Hydrogenphosphonates acylation

The reactions which take place between acetophenone and PCI3 have been revisited. Reactions between diethyl hydrogenphosphonate, (Me3Si)2NM (M = Li, K, or Na), and an acyl chloride RCOCl in the ratio 2 2 1 in THF at —100 °C during periods of only seconds lead to only (155) (R = alkyl) or to mixtures of... 

When NaOMe was employed as catalyst in the initial reaction, the formation of 262 was accompanied by that of significant amounts of the 3-hydroxy-l,2-oxaphosph(V)olanes 263, again as mixtures of diastereoisomers. The latter are also obtained through the tri-ethylamine-catalysed intramolecular transesterification of the linear esters 262 Mixtures of linear and cyclic acylated phosphonic esters, e.g. the acetates of 262 and 263, result when 4-acetyloxybutan-2-one is acted upon by a dialkyl hydrogenphosphonate". ... 

Through the acylation or alkylation of hydrogenphosphonates and related compounds... 

The course of the condensation between an acylphosphonate and a 1-nitroalkane car-banion depends on the nature of the acyl group. Base catalysts are commonly employed, but an acylphosphonate derived from an aromatic acid requires an acidic catalyst otherwise the intermediate anion fragments to hydrogenphosphonate and nitroketone (Scheme 20)207 jYiQ reaction between a nitroalkane carbanion and a dialkyl (trichloroacetyl)phos-phonate results in a rearrangement to phosphate with additional dehydrochlorination (Scheme 21) . ... 

The reaction of acylphosphonate diesters with alcohols was reported early to lead to dialkyl hydrogenphosphonates and carboxylate esters In a more recent systematic study, conditions were developed to use acylphosphonates for the acylation of alcohols. It was found that 1,5-diazabicyclo [5.4.0] undec-7-ene (dbu) is a highly effective catalyst for acylation of alcohols by acylphosphonates. Two special aspects deserve mention (1) /er butyl alcohol could be acylated with diethyl benzoylphosphonate, in the presence of dbu and 4-dimethylaminopyridine, to give r r/-butyl benzoate in 57% yield (2) the primary hydroxy group of a diol (e.g. butane 1,3-diol) could be acylated fairly selectively in the presence of a secondary hydroxy group by this methodology (ratio of mono to diacyl product =88 12). 

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