Bicyclic phosphine oxides

As indicated by their pattern of reactivity,the products of pyrolysis of the Of-diazomethylphosphines (92) are best regarded as nucleophiliccarbenes (93). Some aspects of the reactivity of the bicyclic system (94) have been explored. With chlorodiethylphosphine, the salt (95) is formed, which is converted into the bicyclic phosphine oxide on methanolysis. The phosphine... 

Deoxygenation and Desulfurization. Hexachlorodisilane has been shown to effect the stereospecific reduction of phosphine oxides to phosphines with inversion of configuration (eq 1 ), although short reaction times are required to prevent chemical racemization of the phosphine products under the reaction conditions. This protocol complements trichlorosilane which, under appropriate conditions, reduces phosphine oxides with retention of configuration. Reductions of bridged bicyclic phosphine oxides and cyclic halophospholene oxides by hexachlorodisilane have also been reported. 

The isomeric bicyclic phosphines (41) have been obtained by reduction with trichlorosilane of the related isomeric phosphine oxides, the reaction proceeding with... 

Hydrolysis of 1,1-diphenylphosphorinanium bromide 71 with aq NaOH gave phosphine oxide 72 in 99% yield. Phosphine oxide was further reductively alkylated to 73 using Si(0Et)3H/Ti(0-7Pr)4 with various alkyl bromides <1998SL497> (Scheme 3). Bicyclic phosphines 74 were alkylated to 75 using BuLi/RBr (Equation 4) <2003JCD2036, 2003JCD4669>. 

Mono- and bicyclic phosphorus heterocycles 199, 200, 202, and 203 were synthesized starting from the bifunctional phosphorylating agent bis(diisopropylamino)ethynyl phosphine 195 via ring-closing enyne metathesis using 4,5-dihydroimidazol-2-ylidene ruthenium benzylidene complex, as a catalyst. Bicyclic phosphorus oxides 199 were obtained in 66-83% yield, whereas phosphorus borane derivative 202 was isolated in 74% yield <2001TL8231>. 

Wittig Reaction. The intramolecular Wittig reaction of an ylide obtained from (-P)-CAMP occurred with 77% ee to give the ( -bicyclic diketone. Although a stoichiometric amount of the optically pure phosphine was required, the phosphine oxide (-t)-CAMPO could be recycled. Enantiomeric excesses using CAMP were much higher than similar reactions which employed other chiral phosphines. 

Walkenyl, W-(adenosine-2-yl), and Wphosphoryl bicyclic isoxazolidines were also obtained by HDA reactions of cyclopentadiene with nitroso alkenes, 2-nitrosoadenosine, P-nitroso phosphine oxides and P-nitroso phosphate, respectively <20000L1323, 2001J(P1)1908, 2002JOG6174>. 

The reaction of triethylphosphine with dimethyl acetylenedicarboxylate in the presence of p-chlorobenzaldehyde is reported to lead to the olefin (58) and the bicyclic lactone (59). In the presence of water, the initial dipolar adduct (60) is hydrolysed, with the formation of dimethyl fumarate and the phosphine oxide. ... 

Methyl diphenylphosphinite and u-hydroxycinnamic acid gave the bicyclic acyloxy-phosphorane (52). This rearranged above its melting point to give the coumarin (54) and was hydrolysed rapidly to give the phosphine oxide (53). 

Quin s group have reported the synthesis of a number of tricyclic phospholene oxides, e.g., (9), by the McCormack reaction. The isomeric bicyclic phosphine... 

Scheme 4.52 Preparation of a phosphinate from a bicyclic oxazaphospholidine oxide/ sulfide.

The mechanism and origin of enantioselectivity has been evaluated for a bicyclic guanidine-catalyzed phospha-Michael reaction between diphenyl-phosphine oxide and p-nitrostyrene by DFT calculations (Scheme 32). The catalyst was found to be involved in all three steps of the catalytic cycle proposed. 

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