Propyne Subject

A detailed, extensive review of cyclopropene has appeared. Cyclopropene is the last of the small strained ring hydrocarbons to have its thermal decomposition subjected to intensive investigation.158 Cyclopropenes can decompose by a variety of mechanisms involving diradicals, vinylcarbenes, and vinylidenes. Cyclopropene itself has been shown to be an intermediate in the allene-propyne rearrangement. 

A sample of catalyst was placed in the environmental cell within the FTIR spectrometer, reduced as outlined in the Experimental section, and subjected to a 1 3 propyneidhihydrogen reaction mixture. The bands observed in the various spectra are reported in Table L At no time were any bands observed which indicated the presence of propane and the pressure fall was consistent with the conversion of propyne to propene. 

In the earlier work , 797 was subjected to flash vacuum pyrolysis (500 °C) in the presence of various dienes as traps. For example, with thiophene as a trap the identifiable products were thianaphthene 799 (59%) and sulfur, and with furan, hydroxythianaphthenes 801 (1 %) and cyclopentenothiophenes 802 (8%) were identified. Adducts 798 and 800 could not be detected, and alternative routes to the observed products, as well as to those obtained with other traps (1,3-cyclohexadiene, benzene, cyclopentadiene, 2,3-dimethyl-1,3-butadiene and propyne) were presented. Pyrolysis of797 in the presence of hexafluoroacetone... 

The imine 188, derived from 3-(trimethylsilyl)-2-propynal and (S)-a-methyl-benzylamine, was treated at — 40 °C with the born enolate 187 prepared from S-phenyl butanethioate, 9-borabicyclo[3.3.1]nonyl triflate and DIPEA. After workup, a mixture of the anti p-amino acid 189 and the syn adducts 190 was formed in a 5.2 1 ratio. This mixture was then subjected to cyclization using tert-butylmagnesium chloride in diethylether to give the trans P-lactam 191 in... 

Due to the existence of five-membered furan rings in low-rank coals [49], the pyrolysis mechanism of furan has become the subject of several experimental studies [50-52]. Recently, some detailed theoretical studies have been carried out to understand the formation processes of CO, C3H4 (propyne and aUene), ketene, acetylene, and so on. 

Nickel-catalyzed Carbostannylation. When 3-trimethylsilyl-1 -propyne is subjected to a 1,2-diene in the presence of an alkynyl-stannane and a nickel catalyst, a carbostannylation takes place with high Z-selectivity under the specified conditions. Alternative conditions provided the -isomer as the major product (eq 43). ... 

To palladium acetate (1.8 mg, 7.8 //mol) placed in a Schlenk-type tube under a nitrogen atmosphere is added 1,1,3,3-tetramethylbutyl isocyanide (16.8 mg, 0.12 mmol) under stirring at rt. >eep red color is observed immediately, indicating the formation of active palladium(0)-isonitrile catalyst. To the mixture successively added at rt are toluene (0.1 mL), (dimethylphenylsilyl)(pinacolato)borane (102 mg, 0.39 mmol), and 3-(/er/-butyldimethylsilyloxy)-l-propyne (91 mg, 0.53 mmol). The resulting mixture is heated to reflux for 1-4 h, then cooled down to rt, and finally subjected to a short column chromatography on silica gel (diethyl ether) to remove the catalyst. Further purification by bulb-to-bulb distillation of the crude product gives the title compound in 83% 3deld. 

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