Diethyl benzoylphosphonate

Diethyl benzoylphosphonate, C6H5C—P(OC2H5)2 (1). Mol. wt. 242.20, b.p. 141-147°/ 3 mm. The reagent is prepared by reaction of benzoyl chloride with triethyl phosphite... 

Cool the reaction mixture and replace the condenser with a fractional distillation set up. Distil the product at vacuum-pump pressure, discarding any low boiling fore-run, and collect pure diethyl benzoylphosphonate, 14 (b.p. 141°C, 2.5 mmHg, 15.7 g, 67 %), as a yellowish liquid. 

In the presence of [PdMe2(PMePh2)3] diethyl benzoylphosphonate is degraded during minutes and with quantitative yield, into diethyl phenylphosphonate (l-oxoalkyl)phosphonic esters suffer a similar fate but the process may take several hours under the same conditions. When mixtures of aroylphosphonic diesters and esters of (l-oxoalkyl)phosphonic acids are brought into contact with the... 

A new method of cyclization has been developed, through the reaction of suitably or//ru-substituted diethyl benzoylphosphonates (41), or their acid chloride precursors, with trialkyl phosphites. An analogous reaction takes place with (42) to give the fluorenylphosphonate (43). The mechanism suggested involves initial attack on carbonyl oxygen, and gains support from the formation of the benzofuranylphosphon-ate (45) in the reaction of (44) with triethyl phosphite. 

Hydrolysis of diethyl benzoylphosphonate (84) proceeds by C—P cleavage in both phosphate and imidazole buffers. The rates in the two buffers are... 

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). 

Stoichiometric reactions of diethyl benzoylphosphonate with a variety of amines gave amides 1 as the main products along with diethyl H-phosphonate 2 and a-(phosphoryl-oxy)benzyl phosphonates 3 [235]. The use of hindered diethyl benzoylphosphonate resulted in high yield of amides in the case of primary amines and poorer yields of amides in the case of the reaction with a hindered amine such as diethylamine. 

Dialkyl acylphosphonates are used for acylation of alcohols. Kabachnik [236] reported that dimethyl benzoylphosphonate formed crystalline 1 1 addition products with aUphatic alcohols, which can be converted in the presence of dry hydrogen chloride into carboxylic esters and dimethyl H-phosphonate in moderate yields. Sakurai reported that dialkyl acylphosphonates underwent slow acylation with a large excess amount of alcohols to give esters [237]. It was shown that triethylamine catalyzed acylation of alcohols with dialkyl acylphosphonates [238]. It was found that use of l,5-diazabicyclo[5,4,0]undec-5-ene (DBU) increased the rate of the acylation of alcohols with diethyl benzoylphosphonate dramatically [239]. When one equivalent of DBU was used in CHjClj, the acylation was completed within 10 min and the corresponding ester 1 was obtained in 99% yield. The use of 0.1 equivalent of DBU gave 1 in 95% yield. Under this condition, the formation of 3 was suppressed remarkably and only a trace of 3 was formed. 

An ethereal soln. of diethyl benzoylphosphonate treated with ethereal diazomethane, and the product isolated after 3 days diethyl phenacylphospho-nate. Y 92%. B. A. Arbuzov et al., Izvest. 1963, 675 G. A. 59, 11551d. 

Rhodium(I)/(R)-Segphos complex catalyzed the highly enantioselective [4 + 2] annulation of 2-alkynylbenzaldehyde with diethyl benzoylphosphonate (172) leading to the benzopyranone (173) with a phosphonate-substituted quaternary carbon center (Scheme 60). ° ... 

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