Dimethylacetylene dicarboxylate

In the reaction of 4-substituted 2-aminoselenazoles with ethyl propiolate and dimethylacetylene dicarboxylate. the major products obtained from such a condensation are substituted 7H-selenazolo[3,2-a]pyrimidin-7-ones (5) and not the alternative isomeric substituted 5H-selenazoles[3,2-a]pyrimidin-5-ones (6). Distinction between the alternative structures was based on infrared, ultraviolet, and NMR data (Scheme... 

The seven-membered CN3S3 ring, another ten 7r-electron system, was first obtained as the ester 12.19 (R = COaMe), which is a minor product of the reaction of S4N4 with dimethylacetylene dicarboxylate. It has a planar structure with bond lengths that indicate delocalization. The parent 1,3,5,2,4,6-trithiatriazepine 12.19 (R = H) is obtained as a colourless solid by carefully heating the ester with aqueous HCl followed by decarboxylation. ... 

Cyclopropyl imines can be used as five-atom components in intermolecular [5 + 2]-cycloaddition reactions with dimethylacetylene dicarboxylate (DMAD) (Scheme 14).45 In this hetero-[5 + 2]-cycloaddition reaction, dihydroaze-pines are constructed from simple, readily available starting materials. The cyclopropyl imines can be preformed or made in situ by the condensation of cyclopropyl carboxaldehydes and amines. Although, thus far, DMAD is the only... 

The dimer heated with dimethylacetylene dicarboxylate (DMAD) gives the adduct D, resulting from the addition to the tellurophene moiety of A. The adduct E resulting from the addition to the thiophene moiety of A was not detected. 

The reactions of polysulfido complexes with activated acetylenes have been studied in some detail (4, 5). 1,4- (MeCp2Ti)2(S2)2 reacts with dimethylacetylene dicarboxylate (DMAD) to yield MeCp2TiS2C2R2... 

Tetrahydropyrrolo[3,2-c]pyridines 229 undergo enlargement of the six-membered ring by dimethylacetylene dicarboxylate (DMAD) in acetonitrile, yielding pyrrolo[2,3-d]azocines in moderate yield (02TL6767 Scheme 63). 

Indole reacts with dimethylacetylene dicarboxylate giving tetramethylcar-bazol-l,2,3,4-tetracarboxylate as a major product,formed via 384 (R = H, and/or geometric isomer) and then Diels-Alder addition and dehydrogenation. /V-Acetylindole undergoes an extraordinary double condensation and cyclization with methyl acrylate in the presence of palladium(II) acetate in acetic acid giving 9% of the dimethyl 9-acetylcarbazole-2,3-dicar-boxylate 393 as well as 394 and 395, the products of monosubstitution at the indole a and S-positions. ... 

A number of examples of photoaddition to alkynes has been described. Dimethyl acetylenedicarboxylate has been found to add to methyl-substituted 3-benzoylthiophens301 and to thiophen and 2,5-dimethylthiophen302 on irradiation. Benzo[f>]thiophen also undergoes cycloaddition reactions with alkynes,303 and in the case of dimethylacetylene dicarboxylate, product formation has been shown to be wavelength dependent.304 Intramolecular [ 2 -(- 2] cycloaddition has been observed on both direct and triplet-sensitized irradiation of the alkyne (353) and gives the cyclobutene (354)305 the isomer (355) is formed on prolonged irradiation. 

Allenes react with thiourea to yield thiazine-4-ones, which are further isomerized to 4-oxothiazine-6-ylidene acetic esters (10) (Scheme 8) [(82JCS(P1)1905)]. Acetylenic esters [propiolate and (DMAD)] react with thiourea to give thiazine-4-ones 11 and 12. Substituted thioureas behave like ambident reagents with dimethylacetylene dicarboxylate (DMAD) (Scheme 9) [(69ZOR621 78JCS(P1)1428)]. Finally, the thiazines... 

Some aspects of the reactivity of the A-frames formed by Reaction 1 have been explored. Carbon monoxide and sulfur dioxide are readily lost from the respective adducts upon mild heating or exposure to vacuum. The insertions of isocyanides or sulfur have not been reversed. However the oxidation of Pd2(dpm)2(/Lt-S)Cl2 to Pd2(dpm)2-(/x-S02)Cl2 can be effected by using m-chloroperbenzoic acid as oxidant. Acetylene addition is photoreversible photolysis of Pd2(dpm)2-(/Lt-C2 C02CH3 2)C12 forms dimethylacetylene dicarboxylate and Pd2(dpm)2Cl2 (14). Pd2(dpm)2X2 is a catalyst for converting dimethyl-acetylene dicarboxylate into hexamethyl mellitate, and Pd2(dpm)2-(/it-C2 C02CH3 2)X2, which forms during the reaction, is presumed to be an intermediate. 

Reaction of the nitrilimine derived from C-(2-pyridyl)hydrazonoyl bromide 33 with dimethylacetylene dicarboxylate afforded a mixture of the usual 1,3-dipolar cycloadduct 208 and an unusual cycloaddition product 209 (81H717). 

The homo-Diels-Alder reactions of norbornadiene with dimethylacetylene dicarboxylate (DMAD) and TCNE are reported to have activation volumes of about - 30 cm3 cm-1 and classical examples have already been reviewed [10]. 

The synthetic reactions of nucleophilic carbenes have been reviewed.11 Isonitriles, dimethoxycarbene, and NHCs are covered. The review focuses on the 1,3-dipolar cycloaddition reactions made possible when the nucleophilic carbene reacts with electrophiles such as dimethylacetylene dicarboxylate. Such reactions were also the subject of research papers during 2005 (see the section on nucleophilic and basic carbenes). 

An alternative synthesis of 295 involves (175) the addition of diisoamyl-lithium cuprate to dimethylacetylene dicarboxylate. The major product (89%) was the required 295 together with some 297. The mixture was separated by chromatography. 

The more activated TpRe(CO)(MeIm)(r/2-anisole) complex has demonstrated a slightly broader range of reactivity by undergoing cycloadditions with both N-methylmaleimide (Scheme 13) and dimethylacetylene dicarboxylate (DMAD) (Scheme 14). Analysis of these reactions is complicated by the fact that the initial anisole complex exists as a 3 1 mixture of... 

The aryl-substituted pteridine-5-oxide derivative (32) with dimethylacetylene dicarboxylate (DM AD) in a 1,3-dipolar cycloaddition reaction gave a mixture of the 8-aryldimethylxanthine (33) and the pyrrolopyrimidine (34) (Equation (3)) <85H(23)2317,88MI711-06). 

The products derived from guanidines show aromatic reactivity. They are strongly nucleophilic and may be brominated and methylated in the heterocyclic ring. Reaction occurs with dimethylacetylene dicarboxylate to form the eight-membered insertion product 85. However, this is possibly produced by a two-step process involving electrophilic substitution of the heteroring rather than direct Diels-Alder addition, and this proposal is supported by the simultaneous formation of the substitution product 86. 

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