Acetylenedicarboxylate

The submitters obtained a yield of 70% when three times the above quantities were used, in which case the diethyl malo-nate was added at a rate of 90 ml. per hour. 

Diethyl ethylidenemalonate has been prepared by heating acetaldehyde, diethyl malonate, and acetic anhydride 2 3 by heating the same reagents plus zinc chloride 4 by treating acetaldehyde and diethyl malonate with sodium ethoxide or piperidine 6 and by heating diethyl malonate, ethylidene bromide, and ethanolic sodium ethoxide.6 

DIMETHYL ACETYLENEDICARBOXYLATE (Acetylenedicarboxylic acid, dimethyl ester) 

To 400 g. (510 ml., 12.5 moles) of methanol (commercial grade) in a 2-1. round-bottomed flask is added in small portions with cooling 200 g. (Ill ml., 2.04 moles) of concentrated sulfuric 

The liquid in the flask is then decanted from the inorganic salt, which is washed with 500 ml. of cold water. The solutions are combined and extracted with five 500-ml. portions of ether. The ether extracts are combined and washed successively with 200 ml. of cold water, 150 ml. of saturated sodium bicarbonate solution (Note 2), and 200 ml. of cold water and then dried over anhydrous calcium chloride. After removal of the ether by distillation from a steam bath, the ester is distilled under reduced pressure from a modified Claisen flask. The yield of ester boiling at 95-98°/19 mm. is 67-82 g. (72-88%) (Notes 3 and 4) 1.4444-1.4452. 

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The acetylenedicarboxylate 17 is a reactive compound and is carbonylated smoothly at room temperature to give the ethanetetracarboxylate 18 as the main product and ethene- and ethanetricarboxylates as minor products. Acetylenemonocarboxylate is converted into the ethanetricarboxylate 19 as the main product with several other products[l8]. 

Dimethyl acetylenedicarboxylate (DMAD) (125) is a very special alkyne and undergoes interesting cyclotrimerization and co-cyclization reactions of its own using the poorly soluble polymeric palladacyclopentadiene complex (TCPC) 75 and its diazadiene stabilized complex 123 as precursors of Pd(0) catalysts, Cyclotrimerization of DMAD is catalyzed by 123[60], In addition to the hexa-substituted benzene 126, the cyclooctatetraene derivative 127 was obtained by the co-cyclization of trimethylsilylpropargyl alcohol with an excess of DMAD (125)[6l], Co-cyclization is possible with various alkenes. The naphthalene-tetracarboxylate 129 was obtained by the reaction of methoxyallene (128) with an excess of DMAD using the catalyst 123[62],... 

As illustrated in Scheme 8.1, both 2-vinylpyrroles and 3-vinylpyiroles are potential precursors of 4,5,6,7-tetrahydroindolcs via Diels-Alder cyclizations. Vinylpyrroles are relatively reactive dienes. However, they are also rather sensitive compounds and this has tended to restrict their synthetic application. While l-methyl-2-vinylpyrrole gives a good yield of an indole with dimethyl acetylenedicarboxylate, ot-substitiients on the vinyl group result in direct electrophilic attack at C5 of the pyrrole ring. This has been attributed to the stenc restriction on access to the necessary cisoid conformation of the 2-vinyl substituent[l]. 

Dimethyl acetylenedicarboxylate (DMAD) has also been used to catalyse gramine alkylations (see Entry 7). It may function by both activating the dialkylamino leaving group and deprotonating the nucleophile[3]. 

Most examples of Diels-Alder reactions reported for both 2-vinyl and 3-vinylindoles involve typical electrophilic dienophiles such as benzoquinone, A"-phenylmaleimide and dimethyl acetylenedicarboxylate (see Table 16.1). T hese symmetrical dienophiles raise no issues of rcgiosclectivity. While there arc fewer examples of use of mono-substituted dienophiles, they appear to react... 

Treatment of 192 with dimethyl acetylenedicarboxylate yields a thiophene derivative (195) when R = Ph and a 2-p3Tidone (1S>6) derivative when R = H (Scheme 100). The proposed mechanism involves the formation of a mesoionic derivative (193) initially further dipolar addition yields adduct 194, the decomposition of which is dependent on the R substituent as described for related compounds (435). ... 

Like pyridines (334), thiazoles undergo addition reactions with dimethyl acetylenedicarboxylate leading to 2 1 molar adducts, the structure of which has been a matter of controversy (335-339). 

Allene can be converted to a tnmer (compound A) of molecular formula C9H12 Compound A reacts with dimethyl acetylenedicarboxylate to give compound B Deduce the structure of compound A... 

Dicyanoacetylene, 2-hiitynedinitri1e, is obtained from dimethyl acetylenedicarboxylate by ammonolysis to the diamide, which is dehydrated with phosphoms pentoxide (44). It bums in oxygen to give a flame with a temperature of 5260 K, the hottest flame temperature known (45). Alcohols and amines add readily to its acetylenic bond (46). It is a powerhil dienophile in the Diels-Alder reaction it adds to many dienes at room temperature, and at 180°C actually adds 1,4- to benzene to give the bicyclo adduct (7) [18341 -68-9] C QHgN2 (47). 

Methylpyridazine gives the pyridazine Reissert compound (105) with trimethylsilyl cyanide and freshly distilled benzoyl chloride. On the other hand, when pyridazine or 3-methylpyridazine reacts with undistilled benzoyl chloride the bicyclic compounds (106) are formed and these react with dimethyl acetylenedicarboxylate in anhydrous DMF to give pyrrolopyridazine derivatives (107 Scheme 30) (81JHC443). 

The reactions of pyrroles with dimethyl acetylenedicarboxylate (DMAD) have been extensively investigated. In the presence of a proton donor the Michael adducts (125) and (126) are formed. However, under aprotic conditions the reversible formation of the 1 1 Diels-Alder adduct (127) is an important reaction. In the case of the adduct from 1-methylpyrrole, reaction with a further molecule of DMAD can occur to give a dihydroindole (Scheme 48) (82H(19)1915). 

Few isothiazoles undergo simple cycloaddition reactions. 4-Nitroisothiazoles add to alkynes (see Section 4.17.7.4). With 5-thiones (84) and dimethyl acetylenedicarboxylate, addition to both sulfur atoms leads to 1,3-dithioles (85) (77SST(4)339, 80H(14)785, 81H(16)156, 81H(16)595). Isothiazol-3-one 1-oxide and the corresponding 1,1-dioxide give normal adducts with cyclopentadiene and anthracene (80MI41700), and saccharin forms simple 1 1 or 1 2 adducts with dimethyl acetylenedicarboxylate (72IJC(B)881). 

Acetylenedicarboxylic acid ester reacts with (184) in benzene-pentene at 20 °C to give the 3 1 adduct (185) (77AG(E)177). 

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