Acetylenic ethers, reactions with phosphine

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... 

Various acetylenes having functional groups such as halide, alcohol, ether, amine, alkene and nitrile, are tolerated in the reaction. An asymmetric (2+2+2) cydoaddition of a,03-diynes with alkyne was achieved by a [IrCl(cod)]2 catalyst combined with a chiral phosphine ligand such as MeDUPHOS and EtDUPHOS, and gave axially chiral aromatic compounds [20]. 

Reactions of several phosphorus-containing nucleophiles with acetylenic esters are reported in the literature. Tertiary phosphines react with acetylenic esters, yielding a variety of products, depending on the reaction conditions. The reaction of triphenylphosphine with DMAD, for example, in ether around —50° gives an unstable 1 2 adduct, formulated as cyclopropenylmethylidenephosphorane (425), which on... 

In Section VILA, the 1,2-addition of a hydrogenphosphonic diester or related compound to an a,j5-unsaturated aldehyde or analogous ketone " " was discussed in relation to the synthesis of (l-hydroxyalkyl)phosphonic diesters. The latter are formed under condition of kinetic control whereas 1,4-addition (the so-called Pudovik reaction), which leads to the (2-oxoalkyl)phosphonic diester occur under thermodynamic controP" ". In general, reactions which involve ethylenic aldehydes, or acetylenic aldehydes or ketones, tend to result in adduct formation across the carbonyl group, whilst ethylenic ketones tend to take part in 1,4-additions and afford 3-oxoalkyl phosphonic (or phosphinic) acid systems 550 34,946-949 consistent with Markovnikov predictions. Such statements are a broad oversimplification, however, at least with regard to the formation of the oxoalkyl phosphonates. In practice, the manner of addition depends on experimental circumstances, the nature and even amount of catalyst and other factors For instance, for the additions of dimethyl hydrogenphosphonate to the ketones 561 ( = 1 or 2) and 559 (R" = H, R = 2-furyl, R = Me), carried out by the addition of a trace of saturated MeONa-MeOH solution to a mixture of reactants in diethyl ether, yielded (within 5 min) the respective 1,2-adducts (1-hydroxyalkylphosphonates) in yields of64,69 and 52% ... 

---