Diphenylsilane/AIBN

Other Methods - The 2,3-unsaturated compound 26, an intermediate in the preparation of an analogue of the antibiotic PA-48153 C (an immunosupressant) was prepared by deoxygenation of the corresponding 2,3-di-xanthate using diphenylsilane-AIBN. (See also Vol. 25, p. 158, ref. 24 for the preparation of a 5,6-unsaturated furanoid derivative using the same technique). ... 

Dideoxygenation of 1,6-Anhydro-D-glucose by the 3-0-Trimethylsilyl-2,4-bis-phenytthionocarbonate 37 Derivative with Diphenylsilane and AIBN [47]... 

A solution of the starting 2,4-bis-thionocarbonate [Eq. (15)] 37 (174 mg, 0.40 mmol), chlorotrimethylsilane (0.31 mL, 2.4 mmol), and triethylamine (0.5 mL, 3.6 mmol) in benzene (3 mL) was stirred for 1 h at room temperature. After filtration, the solvent was evaporated. The residue was dissolved in toluene (1 mL) and diphenylsilane (294 p,L, 1.6 mmol) was added. The reaction mixture was heated to reflux and treated under argon with 150 mL portions of an AIBN solution (262 mg of AIBN in 3 mL of dioxane) five times (at 20 min intervals) under reflux. After evaporation of the solvent under reduced pressure, the residue was analyzed by H NMR to give 85% of the 2,4-dideoxy-3-trimethylsilyl-l,6-anhydro-D-glucose product 38. 

To a solution of the dixanthate (0.185g, 0.4mmol) in dry toluene (3ml), diphenylsilane (147 ml, 0.8 mmol) was added under argon. Then the solution was brought to the boil and treated with portions (300 ml) of a solution of AIBN in toluene (262.4 mg AIBN dissolved in 6.0 ml of dry toluene) at 30 min intervals. The reaction was monitored by TLC. When the reaction was complete (5 h), the solvent was evaporated under vacuum and the olefin isolated by column chromatography on silica gel (eluent CH2C12), giving (1) (93.5 mg, 94%). 

Deoxygenation of primary and secondary alcohols.1 This deoxygenation has been effected by reduction of the thiocarbonyl esters with tributyltin hydride and AIBN as the radial initiator (11, 550). A newer, milder method uses diphenylsilane in a radical chain reaction initiated by triethylborane and air. Even secondary thiono-carbonates, particularly those derived from 4-fluorophenol, are deoxygenated at 25°. 

Hydroxy sulfones can be easily transformed into derivatives for radical-mediated reactions such as thiobenzoates,220 xanthates,221,222 selenoben-zoates,221,222 and thionocarbonates.221,222 These substrates may be used in subsequent stereoselective syntheses of alkenes by free radical methods. Methyl xanthates usually give the best results in the olefination reaction, typically using O-acyl A - It y d roxy- 2 - thiopy ri d o n e under visible light irradiation. Alternatively, diphenylsilane in combination with radical initiators such as Et3B/02, benzoyl peroxide, or AIBN may also be used (Eq. 127).221 222... 

Alkenes from vic-diols Bis(dithiocarbonates) can be converted into alkenes by reaction with tributyltin hydride/AIBN (8,499). Diphenylsilane and an initiator are equally effective and avoid use of toxic tin compounds. This radical reaction gives particularly high yields in reactions of nucleoside derivatives. 

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