Dialkyl silyl phosphites

Similar deprotection procedures have been applied in the last stages of Abramov syntheses, and are illustrated in Scheme 25 with particular reference to the (1,2-dihydrox-ypropyl)phosphonic acid derivatives (R = Me). Dimethyl (2-benzyloxy-l-hydrox-ypropyl)phosphonate is obtainable as a mixture of stereoisomeric forms 290a and b from (Me0)2P(0)H and (5)-2-benzyloxypropanal (289). The aldehyde 289 also reacts with dialkyl silyl phosphites to afford a mixture of the fully protected compounds 291a and b, which may be selectively desilylated or completely deprotected to give the diastereoiso-meric forms of (l,2-dihydroxypropyl)phosphonic acid, 292a and b, also obtainable by the debenzylation of the respective 290" . Dimethyl (l,2-dihydroxyethyl)phosphonate has likewise been obtained in racemic form as its 2-O-benzyl derivative, and also in optically active forms as its l-0-(r rf-butyldimethylsilyl) and 2-0-benzyl-l-0-(r rf-butyl-... 

Sulfuryl chloride fluoride Phosphoromonofluoridates from dialkyl silyl phosphites s. 43, 401 s.a. Tetrahedron Letters 29, 3301-2 (1988). SO.CIF 2 (0)F... 

Thiopyrophosphoric acid esters from dialkyl silyl phosphites (R0)2P(0)SP(0)(0R )2 thiolthiono-derivs. s. 17, 644s42 monothio-derivs. and selenium analogs (selenopyro-phosphorie acid esters) s. J. Chem. Soe. Perkin Trans. I 1988, 2197-201. 

Dolgov, O.N., and Voronkov, M.G., Telomerization of dialkyl hydrogen phosphites and hw(trialkyl-silyl) hydrogen phosphites with vinylsilane derivatives, Zh. Obshch. Khim., 40, 1668, 1970 J. Gen. Chem. USSR (Engl. Transl.), 40, 1660, 1970. 

Symmetrical monothio- and monoselenopyrophosphate esters (36) have been prepared in high yields from dialkyl trimethyl-silyl phosphites and the sulphenyl or selenenyl chlorides (37)... 

The greater nucleophilic reactivity of silyl phosphites towards organohalogen compounds results in a greater complexity in product composition thus, dialkyl trimethylsilyl phosphites and CCI4 afford the dialkyl (trichloromethyl)phosphonates in yields of 50-60%, together with various halogenated silicon-containing products and a dialkyl phosphorochloridate (in up to 30% yield)". ... 

Much attention has been devoted to the conversion of aldehydes into the trimethylsilyl ethers of (a-hydroxyalkyl)-phosphonic acids 210 or analogous -phosphinic acids, or of the corresponding (a-hydroxyalkyl)phosphonic diamides 211 by the use of dialkyl trimethylsilyl phosphite or Me3SiOP(NEt2)2 (or other phosphorodiamidite) It is a reaction which occurs very readily, even at room temperature, and the ready methanolytic or hydrolytic removal of the silyl protecting group makes the procedure an attractive alternative to the direct synthesis of the (a-hydroxyalkyl)phosphonic acids from dialkyl hydrogenphosphonates and carbonyl compounds. Silyl-protected hydroxy-phosphonic and -phosphinic acid derivatives are useful for further synthetic development. ... 

Sodium dialkyl phosphites add to the 4-arylidene-4,5-dihydro-1,3-oxazoles 273 to give the enolate anions 274 on the other hand, the adducts 275—the potential products of the silylation of 274—are more conveniently obtained by additions of dialkyl trimethylsilyl phosphite. The adducts 275 undergo alcoholysis with alcohols, R OH, to give the 2-amino-3-phosphinoylpropanoic acid esters 276, whilst the action of water yields the acids 276... 

An indirect method for obtaining 1-dialkoxyphosphinyl-l-trimethylsilyoxyvinylphos-phonates is through the addition of dialkyl trimethylsilyl phosphite to a,jS-unsaturated aldehydes. When the initial j, 7-unsaturated phosphonates were treated with lithium diisopropylamide (Ida) followed by an electrophile such as an alkyl halide, acyl halide or aldehyde, the corresponding y-substituted silyl enol ethers resulted (equation 90) ... 

Diethyl [(2-tetrahydropyranyloxy)methyl]phosphonate is useful in the Wlttig-Horner synthesis of enol ethers, which are intermediates in one-carbon homologations of carbonyl compounds. This procedure is an adaptation of a general method for making dialkyl hydroxymethylphosphonates. An 0-tetra-hydropyranyl derivative also has been made from dibutyl hydroxymethyl -phosphonate, and diethyl hydroxymethylphosphonate has been O-silylated with tert-butylchiorodimethylsilane and imidazole. Another useful congener in this series has been prepared by an Arbuzov reaction of methoxyethoxymethyl (HEM) chloride and triethyl phosphite. 

Wenzel and Jacobsen reported the thiourea 15b-catalyzed Mannich-type reaction of a ketene silyl acetal with an N-Boc-aldimine, furnishing (3-amino esters with excellent enantioselectivities (Equation 10.30) [59]. Subsequently, Jacobsen and co-workers reported the hydrophosphonylation of dialkyl phosphites with aldimines to yield a-amino phosphonates [60]. 

A one-pot process has been devised for the synthesis of dialkyl [(a-phenylamino)ben-zyljphosphonates from dialkyl hydrogenphosphonate, benzaldehyde and aniline, presumably adaptable for other aromatic amines or aldehydes To avoid multiple reactions of the Mannich type when using a primary amine and a particularly reactive carbonyl component such as formaldehyde, initial silylation of the amine, or the use of diethyl trimethylsilyl phosphite, are valuable moderating variations The amine can be replaced by a carboxamide" or carbamate ester, conveniently the benzyl ester , and the product can then be selectively deacylated with HBr in acetic acid at room temperature or by hydrogenolysis. Alternatively, even a phosphoric amide may be used to afford an A-phos-phorylated product (221)" ... 

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