Allenyl phosphine oxides

To a mixture of 100 ml of dry dichloromethane, 0.10 mol of propargyl alcohol and 0.11 mol of triethylamine was added a solution of 0.05 mol of Ph2PCl in 75 ml of dichloromethane in 3 min between -80 and -90°C. The cooling bath was removed, and when the temperature had reached 10°C, the reaction mixture was poured into a solution of 2.5 ml of 362 HCl in 100 ml of water. After vigorous shaking the lower layer was separated and the aqueous layer was extracted twice with 25-ml portions of dichloromethane. The combined solutions were washed twice with water, dried over magnesium sulfate and then concentrated in a water-pump vacuum, giving almost pure allenyl phosphine oxide as a white solid, m.p. 98-100 5, in almost 1002 yield. 

The cycloaddition of allenes carrying an electron-withdrawing phosphorus substituent has also been studied [118]. Allenyl phosphine oxide 138 is prepared in a manner analogous to allenyl sulfoxide. The [4+ 2]-cycloaddition reaction of 138 with cyclopentadiene proceeded with a high endo selectivity. 

Thus, l-alkynyl-2-methylcyclopentanols react with chlorodiphcnylphosphine in the presence of base to give transient phosphinites, which rearrange stereoselectively to allenyl phosphine oxides I24... 

When an enantiomerically pure alkynol is used, a single enantiomer of an allenyl phosphine oxide 4 with axial chirality is obtained25. 

Allenyl phosphine oxides (75) have been prepared by the reaction of the enediyne alcohols (74) with chlorodiphenylphosphine. When heated at 37°C in the presence of 1,4-cyclohexadiene, (75) gave mixtures of aromatic compounds (76), (77) and (78) (Scheme 12). Evidence for the biradical (79) acting as an intermediate was obtained by heating (75) i n perdeuterotetrahydrofuran. O The enediyne alcohol (74, R = CH2CH20Ac) shows DNA-cleaving activity which is presumably related to diradical formation. ... 

The hydrophosphination of allenyl phosphine oxides with the boranes of secondary phosphines afforded the mixed phosphine oxides - phosphine boranes (Scheme 28). ... 

A review of electrophilic addition for allenes by Ma includes coverage of the iodohydroxylation of 1,2-allenyl phosphine oxides. ... 

Aiming at bifunctionalized allenes, alkynols were phosphorylated with diphenyl-chlorophosphine. The resulting intermediate underwent a spontaneous [2,3]-sigma-tropic rearrangement in the presence of hydrochloric acid as catalyst to afford the corresponding allenyl phosphine oxide that was converted in two steps to the sulfonyl derivative (Scheme 17). ... 

Hydroformylation of allenes (1,2-butadienes) was mentioned only once in the literature. Fell and Beutler [91] reacted allenes with syngas in the presence of HRh(CO)(PPh3)3 but obtained only a mixture of mono- and dialdehydes. In 2008, Guo and Ma [92] used 1,2-allenyl phosphine oxides and phosphonates as substrates and, under the control of the same catalyst, achieved exclusively the production of the terminal aldehydes. 

An interesting approach to allenyl thioethers has been reported by Huang and Xiong, which is based on a novel three-component reaction. Treatment of 1-alkynyl-phosphine oxides 310 with lithium alkylthiolates 311 in the presence of an aldehyde 312 provides the expected highly substituted allenyl thioethers 313 in good yield (Scheme 8.84) [173]. Unfortunately, this procedure could not be extended to arylthio-lates. 

Intramolecular rearrangement of 2-alkynyl phosphites or phosphinites gives allenyl phospho-nates or phosphine oxides, respectively, and in most cases proceeds with high stereoselectivity (cf. Houben-Weyl, Vol. E2, p 19). 

Allenylic-diphenylphosphine oxides have been shown to undergo regioselective iodohydroxylation promoted by the neighbouring group participation of the phosphine oxide functionality (Scheme 27). ... 

The need for a base additive in this reaction implies the intermediacy of acetylide complexes (Scheme 9.10). As in the Rh(III)-catalyzed reaction, vinylidene acetylide S4 undergoes a-insertion to give the vinyl-iridium intermediate 55. A [l,3]-propargyl/ allenyl metallatropic shift can give rise to the cumulene intermediate 56. The individual steps of Miyaura s proposed mechanism have been established in stoichiometric experiments. In the case of ( )-selective head-to-head dimerization, vinylidene intermediates are not invoked. The authors argue that electron-rich phosphine ligands affect stereoselectivity by favoring alkyne C—H oxidative addition, a step often involved in vinylidene formation. 

The catalyst-free and catalyzed addition of >P(0)H species to allenyl-and alkynylphosphine oxide was investigated. The reaction of diphenyl-allenylphosphine oxide with Ph2P(X)H was performed without solvent and catalyst. In this case, the major product was the a-methylene-ethylene(bis-phosphine) derivative, while the methyl-vinyl(bisphosphine derivative) was... 

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