Arbuzov, modified

The free radical Arbuzov reaction has been developed for the preparation of vinyl- and arylphosphonates in good to excellent yields. Oligonucleotides, suitably modified in the vicinity of the phosphorus backbone to impart nuclease... 

The use of arylhydrazones for the synthesis of indoles has been widely discussed in the literature [1,2, 169], One of the most useable methods is the Fischer reaction [169, 170, 171], modified by Arbuzov [172],... 

A modified Arbuzov reaction has been applied to the coupling of the D-glucal/D-galac-tal derived vinyl halides 205 and triethyl phosphite at 150 °C in the presence of NiCl2... 

A consistent dilution procedure may be necessary for reproducible assays. The order of adding reaction aliquot to diluent or vice versa may produce significantly different results. For instance, in the preparation of 18 by modified Arbuzov reaction (Figure 7.5) [10], the phosphonic acid by-product 17 was detected at... 

The start-up of the initial manufacturing process to prepare the phosphinyl acetic acid 6 by modified Arbuzov reaction (Figure 15.4) proceeded as anticipated. Subsequent manufacturing campaigns produced off-colored batches of 6, and the reactions did not proceed to completion [2]. It was known that equal amounts of trimethylsilyl chloride (TMSC1, bp 57°C) and hexamethyldisilazane (HMDS, bp 125°C) were needed for rapid silylation [3], To control the rate and hence exothermicity of the reaction, HMDS had been added to the TSMCl-containing... 

Saady, M., Lebeau, L., and Mioskowski, C., Synthesis of di- and triphosphate ester analogs via a modified Michaelis-Arbuzov reaction. Tetrahedron Lett., 36, 5183, 1995. 

Arbuzov reaction with HP(OSiMe3)2 as the reagent and were converted into the corresponding 3 -methylene modified phosphonamidates using PhsPCb in pyridine. 

Adequate understanding of the mechanism of the Michaelis-Arbuzov reaction has been hampered by a deficiency of thorough kinetic investigation. On the basis of specific volume measurements, Zawidski and Staronka (303) in 1915, and Staronka (291) in 1927, proposed an empirical rate equation to correlate their data. This equation in modified form (eq. 5) has more recently been applied by Isbell and associates... 

Alkyl ethers of dialkyl (hydroxymethyl)phosphonic acid have been obtained by a modified Arbuzov procedure in the presence of BF3 Et20, triethyl phosphite reacts with the formals ROCH20Ar according to Scheme 16 the reactions are best carried out in the presence of TiCl4 at -78 °C, but the Lewis acid catalyst and the experimental conditions have to be chosen carefully, otherwise mixed alkyl aryl esters are produced. Boron trifluoride etherate also catalyses the interaction of acetals of 4-substituted benzaldehydes with triethyl phosphite to give diethyl (a-alkoxybenzyl)phosphonates. Both aliphatic and aromatic aldehydes are reported to react with trialkyl phosphites at 100 °C to give the ethers 204 ... 

Coordinated phosphites may also be modified by metal catalysis to act as nucleophiles. For example, in the nickel-catalyzed Arbuzov reaction [110, 111], after oxidative addition of an aryl halide, attack of free or metal-bound halide at... 

In the area of 2, 3 -didehydro-2, 3 -dideoxycompounds (d4 systems), a previous method for their synthesis from 5 -protected 2, 3 -di-0-mesyl-nucIeosides by treatment with arylselenyl anions (Vol. 31, p. 272) has now been modified by the use of bis(4-perfluorohexylphenyl) diselenide and sodium borohydride, which permits the use of the diselenide in catalytic quantities, and also its ready recovery. The method was used for the synthesis of d4-uridine. Analogues of d4T with potential linker arms at C-5, for attachment of either a fluorescent tag or a non-nucleoside reverse transcriptase inhibitor, have been prepared either from 5-(hydroxymethyl)uridine or from the 2,2 -anhydronucleoside of 5-(methoxycarbonyhnethyl)uridine (Vol. 28, p, 265-266). Addition of iodine at C-2 and C-3 of protected pyrimidine nucleosides under Arbuzov reaction conditions has led to a new route to d4 systems, and d4-uridine has been prepared from 2 -deoxyuridine using elimination from the 3, 5 -dimesylate. ... 

This reaction has been extensively modified. Besides the ruthenium-catalyzed, metal-centered radical or photo-Arbuzov rearrangements as described earlier, alkyl halides have been replaced by metal halides (e.g., NiC ), trimethylsilyl chloride (TMSCl), and organometallics. 

Arbuzov and Michaelis-Becker reactions provide facile and versatile procedures for the formation of carbon-phosphorus bonds. These methods, however, are not applicable to the formation of sp hybridized carbon-phosphorus bonds. Only few methods have been reported for the syntheses of arylphosphonates and vinylphospho-nates. Direct reaction of aryl or vinyl halides with trialkyl phosphite in the presence of nickel halide requires severe reaction conditions [21,22], and the stereochemistry of vinylphosphonates has not been clarified. Synthesis of dialkyl arylphosphonates 22 [23, 24] is achieved by the palladium-catalyzed reaction (Scheme 2.12), which is called by Hirao reaction . The stereoselective synthesis of dialkyl vinylphosphonates 23 [24-26] is similarly accomplished by this method (Scheme 2.13). A variety of modified procedures have been developed recently [27-37]. 

SCHEME 47.5. Stereoselective Arbuzov reaction in the synthesis of modified P-glycosides. 

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