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1.2- Oxaphospholenes reactions

Oxidation of Oxaphospholenes. Reaction of oxaphos-pholene (5) with (+)-[(8,8-dichlorocamphoryl)sulfonyl] oxaziri-dine (2) affords p-hydroxy-y-keto-phosphonate in 49% ee with undetermined absolute configuration (eq 3). Higher temperatures accelerate the reaction but lower the stereoselectivity. [Pg.185]

Dichloroethylphosphine has been shown to react with methyl vinyl ketone to form 2-ethyl-5-methyl-A -l,2-oxaphospholen-2-oxide (25), which has been converted to (26) by chlorination in the presence of base. The same phosphine adds to methyl acrylate in the presence of acetic acid to give the phosphine oxide (27). Further examples have appeared of the reactions of the phenylhydrazones of methyl ketones with phosphorus trichloride to produce the heterocycles (28). [Pg.44]

Preparation of 2,2,2-trimethoxy-3-phenyl-4-acetyl-5-methyl-A4-oxaphospholene — Preparation of an oxyphosphorane by reaction of a trialkyl phosphite with an a,(l-unsaturated carbonyl compound... [Pg.12]

Preparation of diethyl [(2R )-2- l(S )-hy droxyphenyl -3-oxobutyl]phosphonate — Preparation of a functionalized phosphonate by reaction of an oxaphospholene with an aldehyde35... [Pg.162]

In exploring various synthetic methods for the preparation of 1,2-oxaphospholene 2-oxides we investigated the reaction of diacetone alcohol (4-hydroxy-4-methyl-2-pentanone) with methyl and phenylphosphonous dichloride, which was reported (1) to proceed as shown in eq (1) to give 2,3,3,5-tetramethyl-l,2-oxaphos-phol-4-ene 2-oxide or the corresponding 2-phenyl derivative. [Pg.287]

The reaction of trimethyl phosphite with an allenic chloromethyl ketone proceeds with the formation of an oxaphospholene and not through the Michaelis-Arbuzov or Perkow rearrangements. ... [Pg.338]

A related route to 3-oxoalkylphosphonates involves the conjugate addition of trialkyl phosphites to a,P-unsaturated ketones and hydrolysis of the intermediate oxaphospholenes. The utility of this method is enhanced by the nucleophilic character of the intermediate oxaphosphorane, which facilitates the stereoselective aldol reaction resulting in the formation of p-substituted y-ketophos-phonates. - The pentacovalent oxaphospholene reacts with dialkyl azidocarboxylates to give P-hydrazido-y-ketophosphonates in excellent yields. ... [Pg.355]

The usual product, after pyrolysis, is a 1,2-oxaphospholen 2-oxide (32), although an alcoholic work-up yields an acyclic phosphinate (33) (Scheme 10). Just in case these advances in our current mechanistic interpretation of these reactions (c/. ref. 40) leads to complacency, a further Russian paper has described the reactions of acetone and other simple ketones with chlorodiphenylphosphine or chlorodiethylphosphine. These yield the a-chloroalkylphosphine oxide (34), or the derived oxide (35), and not the oxide (36), which is known to be formed from mesityl oxide (28) and chlorodiethylphosphine. a-Halogenoalkylphosphine oxides are generally produced when aldehydes are heated with a wide range of halogenophosphines, and the formation of such an adduct from a ketone is a novel result. [Pg.58]

Reaction of the initially formed acylphosphonate with a second mole of trimethyl phosphite leads to the formation of a cyclic product with one pentacoordinated phosphorus atom. Further reaction of this oxaphospholene with a second molecule of butenoyl chloride, followed by the loss of methyl chloride, leads to the final product. ... [Pg.664]

Synthesis of Phosphonic and Phosphinic Acids and their Derivatives.—The usual batch of papers dealing with the C-phosphorylation of alkenes, 1,2-dienes, 2,3-dienes, and alkynes, - has appeared. Vacuum-dried sodium thiosulphate is an alternative to sulphur dioxide as the reagent for the decomposition of the intermediates formed in such reactions. Further examples of the formation of A -l,2-oxaphospholens from ketones and phosphonous dichlorides have been reported. ... [Pg.110]

Reactions of 2,3-di(methoxycarbonyl)-2/f-azirine with keto-stabilized and ester-stabilized ylides give, respectively, substituted pyrroles and iminophos-phoranes (76). A similar reaction of the ketene-stabilized ylide (77) with 3.3-dimethyl-2-phenyl-l-azirine forms the oxaphospholene (78). ... [Pg.234]

Reactions of diastereomeric mixtures of imino-oxaphospholenes (79a-c) with hexafluoroacetone (80) gave in each case only one diastereomer of each of the bicyclicphosphoranes (81a-c). The structures of (81a) and (81b) were shown by X-ray crystallography to have distorted tbp geometries with the oxygen atoms apical and the O-P-O angles ca. 169°. The compounds were also fully characterised by analysis, mass spectrometry... [Pg.70]

Pentacovalent 2,2,2-triethoxy-2,2-dihydro-5-methoxy-1,2-2 -oxapho-spholene (342) has been synthesized as a new type of enolate from a.jS-nn-saturated ketones (341) and trialkyl phosphites and then hydrolyzed to give a series of phosphonates (343) and (344) (Scheme 77). The aldol reaction of the oxaphospholene intermediate with several aldehydes as electrophiles under mild and neutral conditions produced phosphonate-containing aldol compounds. [Pg.257]


See other pages where 1.2- Oxaphospholenes reactions is mentioned: [Pg.44]    [Pg.1116]    [Pg.12]    [Pg.162]    [Pg.390]    [Pg.395]    [Pg.95]    [Pg.332]    [Pg.83]    [Pg.136]    [Pg.177]    [Pg.8]    [Pg.165]    [Pg.348]   
See also in sourсe #XX -- [ Pg.664 , Pg.665 ]




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1.2- Oxaphospholenes

Oxaphospholens

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