[122289-10-5] · C7H19O3PSi · Diethyl Trimethylsilyl Phosphite · (MW 210.32)
(nucleophilic, trivalent phosphorus reagent capable of forming a diethyl phosphonate derivative by displacement reaction or silylphosphonylation of multiple bond functionalities such as aldehydes and ketones, both saturated and unsaturated1d)
Alternate Name: DTP.
Physical Data: bp 63-65 °C/15 mmHg.
Preparative Methods: generally prepared by reacting the sodium salt of Diethyl Phosphonite with Chlorotrimethylsilane in ether.1a Alternatively, the reagent has been prepared by reacting diethyl phosphonite with chlorotrimethylsilane in ether/TEA.1b
Handling, Storage, and Precautions: is susceptible to hydrolysis and should be prepared immediately prior to use. The salts generated during preparation of the compound are typically removed by filtration and the solution of DTP used without further purification or simply evaporated and the crude material used without purification.
The 1,2-addition of DTP to carbonyl moieties is known as the Abramov reaction. Several reports of this smooth addition reaction have been published. Representative examples are given in Table 1. The initially formed diethyl a-trimethylsiloxyphosphonates are typically isolated via distillation and result from intramolecular transfer of silicon (eq 1).1b
A convenient method to prepare ketones (eq 2)6 and a-hydroxy ketones (eq 3)7 has been developed using these 1,2-carbonyl addition products.
The reaction of DTP with a,b-unsaturated aldehydes, ketones, esters, and nitriles has been reported by several workers.8 In general, reactions with a,b-unsaturated aldehydes occur at rt via a 1,2-addition mode. With Methyl Vinyl Ketone, addition requires heating and occurs in a 1,4-manner. However, 1,2-addition products begin to compete as the steric bulk of the b-carbon increases. To circumvent the forcing conditions required for additions to a,b-unsaturated esters and ketones, a method involving Lewis acid catalysts has been developed using diethyl phosphonite and Trimethylaluminum.9
The reaction of DTP with ketene is exothermic and requires cooling. The resultant [1-(trimethylsiloxy)vinyl]phosphonate can be isolated by distillation (eq 4).3a,8b
With b-dicarbonyl reaction partners, the reaction course is dependent upon the dicarbonyl component. For Ethyl Acetoacetate, an exothermic reaction occurs upon addition of the ester to DTP and the predicted 1,2-addition product is isolated after distillation (eq 5).8c
For 2,4-Pentanedione, multiple products as well as the 1,2-addition product are formed, resulting from competing reactions such as (a) silylation of the enol form of the dione, (b) addition of a second molecule of DTP to the 1,2-addition product, forming an oxaphospholane upon cyclization and loss of methoxytrimethylsilane.10 In the case of ethyl phenylglyoxylate, rearrangement of the initial 1,2-addition product occurs by transfer of the diethyl phosphonate to produce the diethyl phosphate product (eq 6).11
With phenylglyoxylonitrile, an exothermic reaction occurs with DTP to provide a mixture of the phosphonate 1,2-addition product and phosphate rearrangement product. Finally, with a-ketophosphonates such as diethyl acetylphosphonate, straightforward 1,2-addition occurs to provide the bis-phosphonate (eq 7).12
The addition of DTP to epoxides is reported to occur most effectively under Lewis acid (Zinc Iodide, Iron(III) Chloride, Tin(II) Chloride, Tin(IV) Chloride) or basic (n-Butyllithium) catalysis. Reaction generally occurs at moderate temperatures (55 °C), undergoing exclusive ring opening at the terminal carbon.13 This method has been used to prepare fructophosphonic acids (eq 8).14
American Cyanamid, Pearl River, NY, USA