Deoxygenating reagent

The cyclization of 1,5-dicarbonyl chains by means of the deoxygenating reagent triethyl phosphite provides an alternate strategy for building the fused hve-membered penem ring. The first example in fact actually comprises a 1,5-oxa-thio array. Reaction of the perhydrothiophene oxide (16-1) with the anion from carbon disulhde... 

The cobalt analog of the iron dinitrosyl iodide is prepared according to the above procedure with only minor modifications, which are outlined below. Anhydrous deoxygenated reagent-grade acetone and 35.4 g. of cobalt powderf are added to the 1000-ml. flask and allowed to react with the ether solution of iodine (38.1 g. (0.15 mole) of iodine in 300 ml. of ether) over a period of 30 minutes. Then nitric oxide is admitted to the flask. The reaction... 

In the solid phase LR is in the E-form, but in solution the 31P NMR spectrum shows about 10 absorptions showing that different species are present and that precautions should be exercised when considering mechanisms. We now want to report on LR as a thiation reagent and in synthesis of P-heterocycles. It should be noted that LR also reacts with nucleophiles and is a deoxygenation reagent. 

These reactions can be carried out catalytically because the tellurium precipitated during the deoxygenation of the oxiranes will react rapidly with added sodium diethyl phosphite. Lithium 0,0-diethyl tellurolophosphate is a more powerful deoxygenation reagent and is able to convert certain internal epoxides to olefins in a stereospecific manner3. 

Oxazabicyclohexanes (e.g., 106) can be deoxygenated readily under mild conditions to afford the corresponding pyrrolines (e.g., 107). Deoxygenation reagents include thiourea, triphenylphosphine sulfide, potassium thiocyanate, potassium ethylxanthate, and potassium selenocyanate. The 6-tliia-l-azabicyclo[3.1.0]hexanes 135 liave been suggested as possible intermediates in some of these reactions. 

No serious restrictions with regard to the oxygen-accepting organophosphanes PR j seem to apply. While triphenylphosphine is the only well-studied substrate, trialkylphosphines and the water-soluble TPPTS also work (TPPTS = tris(sodium-m-sulfonatophenyl)phosphine cf. Section 3.1.1.1). Other deoxygenation reagents have not yet been employed (e. g., silyl and thio compounds). 

Several mechanisms are possible for these cyclizations. Formation of the dioxide (4) from the unknown 2,2 -dinitrosobiphenyl would parallel the dimerization observed with acyclic nitrosoarenes, and all the other cycliza-tion steps shown in Scheme 1 could be simple condensations, or involve radical anions, or radicals. Where deoxygenating reagents are used, there is also the possibility of cyclization via nitrene intermediates. It has been reported that low yields of benzo[c]cinnolines result from reduction of 2,2 -dinitrobiphenyls with carbon monoxide in the presence of iron penta-carbonyF or by heating in triethyl phosphite. In polarographic reduction studies, Ross et al - claimed to have demonstrated the sequence ... 

The following manipulations are all done in an atmosphere of dry nitrogen using dry, deoxygenated, reagent-grade solvents. Coleman Instrument Grade (99.99% minimum) carbon dioxide is used. Dmpe is commercially available. 

To date there are no reported examples of the above molecules catalyzing a reaction, however Lacote, Curran et al. recently demonstrated that their NHC-stabilized boryl radicals (85, vide supra) can serve as radical initiators for acrylate polymerizations, radical deoxygenation reagents, radical reductions of alkyl halides and radical chain homolytic substitution reactions. ... 

Tertiary phosphines are used widely as deoxygenating reagents in preparative coordination chemistry. Their reactivity toward the oxygen atom is due to the high energy of the P=0 bond in the corresponding phosphoranes (120-150 kcal/mol).i33 Chart was one of the first to use tertiary phosphines as... 

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