Acetylenedicarboxylic esters reaction

Reaction of the mesoionic oxazolone 620 with acetylenedicarboxylic ester 621 gave the cycloadduct 622 in aprotic solvents and the Michael adducts... 

These reactions are found to be promoted by electron-donating substituents in the diene, and by electron-withdrawing substituents in the alkene, the dienophile. Reactions are normally poor with simple, unsubstituted alkenes thus butadiene (63) reacts with ethene only at 200° under pressure, and even then to the extent of but 18 %, compared with 100% yield with maleic anhydride (79) in benzene at 15°. Other common dienophiles include cyclohexadiene-l,4-dione (p-benzoquinone, 83), propenal (acrolein, 84), tetracyanoethene (85), benzyne (86, cf. p. 175), and also suitably substituted alkynes, e.g. diethyl butyne-l,4-dioate ( acetylenedicarboxylic ester , 87) ... 

Such reactions occur readily with alkynic esters, but the products isolated are often complex. Thus, the initial Michael adduct of type (68) from pyridine with acetylenedicarboxylic ester reacts with more alkynic ester to yield (66), (67) and other products. Quinoline and isoquinoline react similarly. 

Diels-Alder reactions of thiophene 1,1-dioxides are very common (B-67MI31401). With rare exceptions, the adduct loses a molecule of SO2 to form a diene which may add another molecule of the dienophile. The sequence with maleic anhydride is shown in Scheme 193. It has been claimed that in the reaction of thiophene dioxide with acetylenedicarboxylic ester the primary adduct could be isolated, but this could not be substantiated (75RTC85). 

The reaction of 1,8-naphthylenediamine with acetylenedicarboxylic ester leads to the mixture of compounds 519-521. The major products of this reaction are compounds 520 and 521, whereas 1,4-diazepine derivatives 519 are formed in a yield of 1% only (86MII). Structure 522 proposed for one of the products is incorrect (NK2161,62NKZ597 83BCJ2338 86MI1). 

Pyrroles can be -alkenylated by reaction with acetylenedicarboxylic ester, for example, to give an /Z mixture (1 3.3) of alkenes 110 (Scheme 48) <2006JOC7793>. 

Three reactions, which were known from the literature to be catalyzed by Lewis acids were selected as test reactions. A, was the Reetz alkylation of silyl enol ethers with -butyl chloride for which titanium tetrachloride is known to be useful [52]. B, was the Diels-Alder reaction between furan and acetylenedicarboxylic ester for which aluminium trichloride is a good catalyst [53]. C, was a Friedel-Crafts acylation for which aluminium trichloride is the preferred catalyst [54]. The reactions are summarized in Scheme 6. 

Reaction of thione 276 (R = H) with diethyl acetylenedicarboxylate in acetic acid or ethanol similarly gives both thiazolidinone (277) and thiazinone (278) as expected (79TL53) (Scheme 67). Condensation of 276 (R = Me, Cl, NO2, CO2H) and 280 with acetylenedicarboxylic esters gives a cyclized product in each case for which respective thiazolidinone structures 279 and 281 were assigned (77M11). This work warrants reinves-... 

Acetylenedicarboxylic ester, propiolic esters and dicyanoacetylene react with unactivated ene components below 200 Isobutene undergoes ene reactions with dimethyl acetylenedicarboxylate... 

Only in exceptional cases is it possible to isolate the enol ether, as with the addition of methanol to acetylenedicarboxylic esters [43], in good yields (eq. (19)). Catalysts which have been used in this reaction are palladium chlorides and platinum chlorides with bidentate phosphine ligands. 

The products contain the metal in a five-coordinated environment, with a chelating amide carbonyl group (CONMe2) for the latter. Reactions (c) and (d) occur at — 78°C at ambient temperature and, in contrast to group IVB derivatives MesMNMcz, even a trace of amide caused polymerization or polycondensation of the acetylenedicarboxylic ester. 

Reactions of Phosphines. - 1.2.1 Nucleophilic Attack at Carbon. Interest has continued in developing the synthetic applications of the 1 1 adducts of tertiary phosphines with dialkyl acetylenedicarboxylate esters. Protonation of the initial adduct from triphenylphosphine by phthalimide, followed by nucleophilic addition of the nitrogen of the resulting imido anion to the intermediate vinylphosphonium salt, has given the stabilised ylide system (189). ° Similar reactions with isatin and 3-chlorotetrahydrofuran-2,4-dione have given the yl-... 

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