Allenic phosphine oxides

The reaction of monoacylhydrazide with 1,2-allenic phosphine oxide 148 afforded /f iminylphosphine oxide 150. Here the unreacted C=C bond in the aUylic phosphine oxide 149 tautomerized to form a C=N bond during the reaction (Scheme 10.72) [77]. 

The intermediate product 162, formed from the nudeophilic addition of 1,2-alle-nic phosphonate or 1,2-allenic phosphine oxide with allylic alcohol, would also undergo a Claisen rearrangement to form 2-oxo-5-alkenyl phosphonate or phosphine oxide 163 [85], The rearrangement is accelerated by the carbanionic nature of the intermediate 162. For the conjugate addition step, the reaction temperature is crucial since the reaction at 0 °C afforded mainly /i,y-unsaturated product whereas a,/8-unsaturated products were formed at 20 °C. 

Likewise, a systematic use of such anisotropy effects has been used to establish the conformation of small rings from the proton shielding in the corresponding allenic phosphine oxides,<1967,153tol56 1968,46 1969 164 to 166) for example in 170. 

A series of N-propargylaminophosphines (15)—(19) has been prepared in order to study their propensity to rearrange (15)—(17) were thermally stable, but (18) and (19) rearranged spontaneously to the A-methyl-3-phosphinopro-penal imines (20) and (21), respectively. This contrasts with the behaviour of the analogous propargyloxy compounds (22) which give allenic phosphine oxides. ... 

An efficient procedure for the synthesis of 2-pyrazolines from unsaturated hydrazone derivatives obtained from allenic phosphine oxides and acethy-drazide or benzhydrazide was described. ... 

J. Berlan and K. Koosha, J. Organometallic Chem., 1978,152,359 ibid., 153,99,109. Me2CuLi and allenic phosphine oxides, carbonyls, sulphones, sulphoxides. 

Methoxyallene has previously been used to prepare acetylenes via its reaction with Grignard reagents, in the presence of copper(i) halides.The use of preformed dialkylcuprates, however, gave the vinyl ethers instead. The E Z ratio varied with the substituent but it is difficult to explain why the difference is observed.Methoxyallene has also been converted into its vinyl anion and used in the synthesis of dihydrofurans and furans in an analogous way to ordinary vinyl ethers.Similarly allenic cuprates have been prepared and used in the synthesis of allenes and allenic pheromonessome examples are outlined in Scheme 58. The addition of lithium dimethylcuprate to allene phosphine oxides and allenic ketones was interpreted in terms of a 1,2- rather than a 1,4-addition process, in contrast to a/3-unsaturated... 

Quantitative yields of allenes were obtained from keten and the stable phosphoranes (48). Addition of similar phosphoranes occurred at the j3-position of the allenic ketones (49) to give the phosphoranes (50). The compound (50 = COPh) eliminated phosphine oxide under the... 

The asymmetric synthesis of allenes via enantioselective hydrogenation of ketones with ruthenium(II) catalyst was reported by Malacria and co-workers (Scheme 4.11) [15, 16]. The ketone 46 was hydrogenated in the presence of iPrOH, KOH and 5 mol% of a chiral ruthenium catalyst, prepared from [(p-cymene) RuC12]2 and (S,S)-TsDPEN (2 equiv./Ru), to afford 47 in 75% yield with 95% ee. The alcohol 47 was converted into the corresponding chiral allene 48 (>95% ee) by the reaction of the corresponding mesylate with MeCu(CN)MgBr. A phosphine oxide derivative of the allenediyne 48 was proved to be a substrate for a cobalt-mediated [2 + 2+ 2] cycloaddition. 

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. 

Type I (fast homodimerization) Terminal olefins, allylsilanes" Terminal olefins, allylsilanes," 1° allylic alcohols, ethers, and esters, " allyl boronate esters, allyl halides, alkyl-substituted allenes Terminal olefms, allyl boronate esters, 1° allylic alcohols, ethers, and esters,styrenes (no large ortho substit.), " " allyl allylsilanes, allyl sulfides, allyl phosphonates, " allyl phosphine oxides, protected allylamines ... 

The double phosphinylation of propargylic alcohols with diphenylphos-phine oxide to form 2,3-bis(diphenylphosphinyl)-1-propenes is catalyzed by a thiolate-bridged diruthenium complex (Scheme 28) [69]. It has been shown that the reaction proceeds via three ruthenium-catalyzed transformations propargylation of the phosphine oxide, alkyne to allene isomerization, and addition of phosphine oxide to the allene structure. 

Nicolaou, K. C. Maligres, P. Shin, J. De Leon, E. Rideout, D. DNA-cleavage and antitumor activity of designed molecules with conjugated phosphine oxide-allene-ene-yne functionalities, J. Am. Chem. Soc. 1990,112, 7825-7826. Schmittel, M. Kiau, S. Strittmatter, M. Steric effects in enyne-aUene thermolyses switch from the Myers-Saito reaction to the —C -cyclization and DNA strand cleavage, Tetrahedron Lett. 1996, 37, 7691-7694. 

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

The Myers-Saito cyclization was first described independently in 1989 by Isao Saito (Kyoto University, Japan) and Andrew G. Myers (California Institute of Technology, Pasadena) whose findings were submitted for publication on June 7 and June 12, respectively. As a parallel transformation to the Moore cyclization (Chapter 4.12), in which an allenic fragment replaces the ketene moiety in the substrate, the Myers-Saito reaction provides a path to carbon diradicals. In its pioneering version, the reaction involved the cyclization of (Z)-l,2,4-heptatrien-6-yne (enyne-allene) 3, or its phosphine oxide derivative 5, to substituted a,3-dehydrotoluene diradicals, and subsequently to toluene derivatives 4 and 6. The reaction proceeds under thermal neutral conditions in 1,4-cyclohexadiene or other organic solvents such as methanol or carbon tetrachloride. 

Allene-enyne thermal Myers-Saito cyclization of [(4Z)-8-tert-butyIdimethylsilyloxy-l-(tert-butyldimethylsilyIoxymethyI)octa-l,2,4-trien-6-yn-l-yl](diphenyI)phosphine oxide (79) 2- tert-butyldimethyl-silyloxy-l-[2-(tert-butyldimethylsilyloxymethyl)phenyllethyl (diphenyI)-phosphine oxide (80) "... 

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. 

Petrov and coworkers [41] showed that the reaction of dibromides of alkenephos-phonic acids with acetylenic alcohols involved an acetylene-allene rearrangement. The products so formed hydrolyzed easily to the corresponding phosphinic acids. The latter on heterocyclization afforded 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives (Scheme 11). 

The diboration of allenes afforded another series of allylboron compounds that each have a boryl group at the vinyl carbon. The addition had a strong tendency to occur at the internal double bond of terminal allenes such as 1,2-heptadiene (Equation (33)).237 However, steric hindrance in both allenes and phosphine ligands forced the addition toward the terminal double bond of dimethylallene (Equation (34)).237 On the other hand, addition to the terminal double bond occurred selectively for both monosubstituted and 1,1-disubstituted allenes when Pd(dba)2 was used in the presence of a co-catalyst (RI) such as I2, Arl, and iodoalkenes (Equation (35)).238 The role of co-catalyst was attributed to in situ formation of I-Bpin intermediate, which undergoes oxidative addition and insertion leading to 2-boryl-7r-allylpalladium intermediate. 

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