Silyl phosphites

Silyl phosphite Silyl phosphonite Silyl phosphinite ... 

Me3Si)2NH, Me3SiCl, Pyr, 20°, 5 min, 100% yield. ROH is a carbohydrate. Hexamethyldisilazane (HMDS) is one of the most common sily-lating agents and readily silylates alcohols, acids, amines, thiols, phenols, hydroxamic acids, amides, thioamides, sulfonamides, phosphoric amides, phosphites, hydrazines, and enolizable ketones. It works best in the presence of a catalyst such as X-NH-Y, where at least one of the group X or Y is electron-withdrawing. ... 

In this context, it is interesting to note that the first synthesis of 2, 3 -0,0-cyclic phosphorothioate 22a was reported by Eckstein in 1968 [25], He also isolated pure Rp diastereomer by fractional crystallization of the triethylammonium salts [26] and used it as reference to determine the absolute configurations of the other phosphorothioate analogues [27], 2, 3 -0,0-Cyclic H-phosphonate 20a was used as a key substrate for the synthesis of uridine 2, 3 -0,0-cyclic boranophosphate 27. Silylation of H-phosphate 20a gave the phosphite triester 25 (two diastereomers). Its boronation, with simultaneous removal of the trimethylsilyl group, was achieved by its reaction with borane-A.A-diisopropylethylamine complex (DIPEA-BH3). 

Preparation of tris(trimethylsilyl) phosphite — Preparation of a silyl ester of a trivalent phosphorus acid for Michaelis-Arbuzov reaction... 

Preparation of 2,3-dioleoyloxypropylphosphonic acid — Reaction of an alkyl halide with a silyl phosphite ester... 

Preparation of [l-(diethoxyphosphinyl)ethoxy]dimethyl-silane — Reaction of an aldehyde with a trialkyl phosphite in the presence of a silyl halide... 

Reaction of a mixed silyl—alkyl phosphite with an aldehyde... 

Several methods for the preparation of the parent compound in this system, tris(trimethylsilyl)phosphite, have been reported.114 118 The application of this and related reagents in reaction with alkyl halides has been reported and used for the preparation of a variety of phosphonic acid analogues of phospholipids.114119-124 Interestingly, alkyl chlorides appear to be more reactive with the silyl reagents than do alkyl iodides, a reversal of the normally observed trend with alkyl esters of the phosphorus acids. (The particular use of silyl phosphorus reagents for the synthesis of biologically significant compounds has... 

Symmetrical cyclic triazines (masked imines) have been used in reaction with diethyl trimethylsilyl phosphite to provide phosphonates bearing silyl-substituted a-aminophosphonates.349... 

Sekine, M., Yamagata, H., and Hata, T., Silyl phosphite equivalents 2,2,2-trichloroethoxycarbonylphosphonates, Chem. Commun., 970, 1981. 

Sekine, M., Okimoto, K., Yamada, K., and Hata, T., Silyl phosphites. 15. Reactions of silyl phosphites with a-halocarbonyl compounds. Elucidation of the mechanism of the Perkow reaction and related reactions with confirmed experiments, /. Org. Chem., 46, 2097, 1981. 

Malenko, D.M., Simurova, N.V., and Sinitsa, A.D., Synthesis of phosphoryl-ated oxiranes from silylated dichloroacetylacetone and triethyl phosphite, Zh. Obshch. Khim., 63, 943, 1993. 

Nucleophilic Reactions.—Attack on Saturated Carbon. Selected examples of the Arbusov reaction include phosphorylation of the chloroacetophenones (1) to give phosphonates, which cyclized to (2) in the presence of acid chlorides,1 formation of the azodiphosphonate (3) from 2,2 -dichloro-2,2 -azopropane,2 3 and the reaction of 2-chloro-3,4-dihydro-3-oxo-2//-l,4-benzothiazine (4) with triethyl phosphite to give the 2-phosphonate (5), which is used as an olefin synthon.8 Bis(trimethylsilyl) trimethylsiloxymethylphosphonite (6) has been synthesized by silylation of hydroxy-methylphosphonous acid, and, as expected, undergoes a normal Arbusov reaction with alkyl halides to give the phosphonates (7).4 This series of reactions, followed by... 

Both mechanisms explain the complete retention of configuration at silicon because free silyl radicals are not involved. The 16-electron complex may add both one phosphite molecule (when it is present in excess) or one carbonyl (formed in the first steps and remaining in solution before being slowly evolved). 

The phosphitylation procedure activated by tetrazole led to the phosphite structure (step a) which was effectively oxidized by TBHP to yield the corresponding phosphate (step b). Finally all 2-cyanoethyl protecting group were removed by the action of DBU in the presence of the silylating reagent bis(trimethylsilyl)acetamide BSA (step c). The latter is indispensable to secure total deprotection. 

The reactions of various l-(l-alkynyl)cyclopropanols were examined using 5-10 mol% of Co2(CO)8 and 10 mol% of tri(o-isopropylphenyl) phosphite. 1-Phenylethynylcyclopropanol (11b), as well as the alkyl- or silyl-substituted derivatives, gave the corresponding 3-substituted 2-cyclopentenones in good to high yields (Scheme 13). 

Five years later, the same authors reported an improved total synthesis of arcyriaflavin A (345) starting from the TBS enol ether 1490 (for the synthesis see Scheme 5.252). This route involves two indolizations based on silyl enol ether nucleophilic attack and Fischer processes. Using Cadogan s procedure by heating in triethyl phosphite, the TBS enol ether 1490 was transformed into the ketone ( + )-1495, involving silyl enol ether-mediated indolization. Finally, Fischer indolization of (+ )-1495 by reacting with phenylhydrazine (524) led directly to arcyriaflavin A (345) in 57% yield (794) (Scheme 5.253). 

Triaryl phosphite-ozone adducts, 706 Tri( -butyl)silyl peroxides, bis(trimethylsilyl) peroxide reactions, 796 Trichloroacetyl chloride, from tetrachloroethene, 731... 

Hydroperoxylation of silyl dienol ethers was effected by the in t7/ -generated reagent triphenyl phosphite ozonide (Equation 26). The yields are moderate and the products are always accompanied by the hydroxylated equivalents. The mechanism was studied and it was found that the oxygen attached to the carbon came from the central O of the ozonide <2001JOC3548>. 

Matsuda independently developed an alternative procedure for the cyclization/silylformylation of enynes that did not require the use of phosphite ligand, and which was effective with low catalyst loading. As an example, reaction of a benzene solution of acetal 65 (0.1 M) and dimethylphenylsilane catalyzed by Rh(acac)(GO)2 (0.005 mol%) under GO (20 bar) at 90 °G for 14 h formed silylated alkylidene carboxaldehyde 66 in 89% yield (Equation (44)). 

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