Allenylphosphine oxides

Fig. 8 Structures and proposed mechanisms of synthetic enediynes 1 cyclodecaenediyne diol, 2 propargylic sulfones, 3 allenylphosphine oxide...

The addition of terminal alkynes to allenylphosphine oxides is catalyzed by palladium complexes (Equation (194)).157... 

The use of chlorodiphenylphosphine to induce a [2,3]-sigmatropic rearrangement of enediynyl propargylic alcohols is one of the first synthetic methods adopted for the preparation of enyne-allenes. For instance, treatment of 108 with chlorodiphenylphosphine and triethylamine at -78 to 0°C afforded the enyne-allenylphosphine oxide 109 in 63% isolated yield (Scheme 20.23) [9]. Thermolysis of 109 at 37 °C in the presence of 1,4-CHD generated the biradical 110, leading to 111 and combina-... 

The enyne-allenylphosphine oxides 120 and the benzannulated and naphthannu-lated analogs 121 and 122 having the diphenylphosphinyl group at the allenic terminus were readily prepared from the corresponding enediynyl propargylic alcohols 117,118 and 119 (Scheme 20.25) [64]. Without the unfavorable steric interactions, these conjugated derivatives smoothly underwent the Myers-Saito cyclization reaction. 

Scheme 20.2S Synthesis and cyclization of enyne-allenylphosphine oxides.

In the addition of Me CuLi reagents to electron-deficient acetylenes [85-88] DCD-type complexes have been identified by NMR [84 89]. As shown below, an ynoate affords a vinylcopper intermediate, while an ynone instead affords an aUenolate (Eq. 10.9). The origin of this diversity remains undear. A rdated carbocupration mechanism has also been proposed for the reaction with allenylphosphine oxide [53]. Olefin carbocupration of dienes [90] and cydopropenes [34, 36] is known, but these mechanisms also remain undear. 

The reactions of allenylphosphine oxides leading to five-membered phosphorus heterocycles have been reviewed. ... 

The chemo- and regioselective semihydrogenation of an 1,2-allenylphosphine oxide and related compounds was accomplished in the presence of a Pd[bis-(arylimino)acenaphthene](alkene) catalyst (Scheme 38). ... 

A regioselective hydroformylation-hydrogenation of 1,2-allenylphosphine oxides was also described in the presence of a rhodium catalyst (Scheme 28)." ... 

Rubin, M., Markov, J., Chuprakov, S., Wink, D.J and Gevorgyan, V. (2003) Highly regiocontrolled Pd-catalyzed cross-coupling reaction of terminal alkynes and allenylphosphine oxides. Journal of Organic Chemistry, 68(16), 6251-6256. 

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... 

Phenolic and benzylic allenylphosphine oxides were cyclized to phos-phinoyl benzofurans and isochromenes, respectively. The conditions applied were, however, different (Schemes 58-1 and 58-2). ... 

Propargylic substitution forming propargyldiphenylphosphine oxide [46] is likely to be the first process, which is followed by isomerization to allenylphosphine oxide and branched-selective addition of a second HP(0)Ph2 (Scheme 45). Direct addition to the propargyldiphenylphosphine oxide is less likely since allenylphosphine oxides can be isolated and other simple alkynes such as 1-hexyne and phenylacetylene are inert toward hydrophosphinylation. 

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