Reductive deoxygenation etherate

Among the more unusual modes of epoxide reactivity is a technique for reductive deoxygenation using a system of triphenylphosphine and iodine in dimethylformamide (DMF). Under these conditions, the functionalized epoxide 98 was quantitatively converted to the diallyl ether 99. Similar conditions were found to convert epoxides to the interestingly substituted (5-bromoformate derivatives (e.g. 101) <02T7037>. 

Thus, as shown by the example in Scheme 42, sequential treatment of the trime-thylsilyl ethers of a variety of tertiary alcohols with oxalyl chloride and the parent thionohydroxamic acid furnishes mixed oxalate esters which undergo reductive deoxygenation on subsequent reaction with a tertiary thiol in refluxing benzene [46]. The selectivity of this method for tertiary alcohols arises as a consequence of the relativity slow rates of decarboxylation of primary and secondary alkoxycarbonyl radicals. 

As with the similarly polarized boron and aluminium hydrides, hydrido-silanes can transfer formal hydride ions to electropositive carbon centres. Unlike the first two reducing agents, hydridosilanes require additional activation of the carbon centre by Lewis or protic acids before such hydride transfer can take place. This overall process is known as ionic hydrogenation (4). The reagent system of triethylsilane and boron trifluoride etherate has provided an extremely selective method for the reductive deoxygenation of lactols (5), derived in turn from DIBAL reduction (6) of the corresponding y- or 6-lactones ... 

Reductive deoxygenation of esters. Under irradiation, esters of nonprimary aliphatic alcohols are reduced to ethers and hydrocarbons (equation I). The relative amounts of the two products are profoundly affected by the R group. ... 

Reductive deoxygenation of cyclododecanyl pivalate by photolysis in the presence of trichlorosilane gave a mixture of cyclododecane and cyclododecanyl,2,2-dimethyl-propyl ether.The disulphonimide (350) reacts with DMSO and sodium bicarbonate to give a mixture of cyclododecenes (88 %) together with cyclododecanone (5... 

Form Supplied in colorless liquid not commercially available. Analysis of Reagent Purity IR (tf) 2955,2900,1935,1250,1210, 1055,840,800,750, and 690 cm H NMR (60 MHz, CDCI3) 50.15 (s, 9H),4.27 (d, 2H, /= 7.7),4.88 (dd, IH,7= 6.6,7.7). Preparative Method two methods have been reported for the preparation of (trimethylsilyl)allene [(TMS)allene] (1). Reductive deoxygenation of the tosylhydrazone derivative affords the title compound in 51% yield. The tosylhydrazone is readily prepared from the corresponding aldehyde, which in turn is accessed by formylation of (trimethylsilyl)ethynylmagnesium bromide with DMF (eq 1). (TMS)allene has also been prepared by flash vacuum pyrolysis of methyl (trimethylsilyl)-propargyl ether, which is obtained from silylation of methyl propargyl ether (eq 2)7... 

Reductive detelluration of aryldichlorotellurolactones (general procedure) f To a solution of the dichloroteUurolactone (1 mmol) in deoxygenated toluene, (10 mL), under reflux and N2, is added dropwise BujSuH (4 mmol). The reaction is monitored by TLC. After 4 h the solvent is evaporated and the residue chromatographed on Si02 (eluted first with petroleum ether to remove Te and Sn by-products, and then with petroleum ether/EtOAc, 1 5), giving the tellurium-free lactone. 

The deoxygenation of phenyl esters and ethers can be achieved by electrochemical reduction provided the fimetion is converted into a good leaving group. 

The present preparation illustrates a general and convenient method for a two-step deoxygenation of carbonyl compounds to olefins. Related procedures comprise the basic decomposition of p-toluenesulfonylhydrazones, the hydride reduction of enol ethers, enol acetates, enamines, the reduction of enol phosphates (and/or enol phosphorodiamidates) by lithium metal in ethylamine (or liquid ammonia),the reduction of enol phosphates by titanium metal... 

Lactones - ethers, y- and (5-Lactones can be converted into tetrahydrofuranes and tetrahydropyrancs, respectively, by a two-step procedure. The first step is the well-known reduction of lactones to lactols with DIBAH (1, 261 2, 140). The second step is deoxygenation of the alcohol with triethylsilanc and BF3 etherate.1 This reaction is compatible with several other functional groups, even including hydroxyl groups. 

The next step was reduction of the ester and O-benzyl ether groups in 6 with lithium in liquid ammonia. Note how the allylic alcohol survived these reduction conditions. Sometimes, allylic deoxygenation can... 

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