Dimethylacetylene

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. ... 

Acetylen 1932 bis 1952, 1956 (14) Dibromacetylen 1936 Vinylacetylen 1939 Dimethylacetylen 1939 Propargylchlorid 1942 Propargylbromid 1942 Propargyljodid 1942 Acetylencyanid 1950 MW,... 

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... 

Azolium systems with C-H bonds can be deprotonated to give rise to an internal azolium ylide or an isoelectronic stable azole carbene system, whereas fully substituted heterocycles such as 142 can evolve in a more complex manner under basic conditions or with nucleophiles. Thus, in the presence of cyanide ion, the formation of adduct 143 could be evidenced by NMR spectroscopy. This intermediate, when stirred at ambient temperature for 48 h in the presence of dimethylacetylene azodicarboxylate (DMAD), led to the adduct 146 (28%) along with products 148 (40%) and 149 (12%) (Scheme 14) <1997JP12919>. 

Tetramethyl-3-4-dichlor-cyclobuten-l (III) bildet sich nach Smirnow-Samkow (221) bei der Einwirkung von Sulfurylchlorid auf Dimethylacetylen. Uber den Mechanismus dieser interessanten Reak-tion liegen noch keine naheren Untersuchungen vor. Fluorierte Deri-vate des Cyclobutens werden auf S. 456 besprochen. 

They have also demonstrated a reversible photochemical conversion from a tridentate to a bidentate B3H8 (Fig. 14). Fehlner has achieved a photochemical carborane synthesis by irradiating mixtures of B4H8Fe(CO)3 and dimethylacetylene. Products of the reactions include (CH3)4C4B4H4 and (CH3)8C8B4H4. Leyden and co-workers have observed two examples of metalloborane isomerization reactions initiated by light ... 

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... 

---