A new general method for the generation of (alk-1-ynyl)halocarbenes by base solvolysis of 3-substituted 1,1,1,3-tetrahalopropanes

Ethynylhydroxycarbene (H–C≡C–C̈–OH)

“…In general, ethynylcarbenes are relevant in astrochemical processes , and can even be used synthetically. − The electronic structure of parent ground-state triplet propynylidene (HCCCH) has been explored in numerous experimental and computational studies with the result that both terminal carbons are equivalent in terms of their reactivity. − The photoreaction of propynylidene with triplet dioxygen provides another entrance channel to the C 3 H 2 O PES as shown in a study by Wierlacher et al, who observed 2 besides the corresponding dioxirane and carbonyl oxide . Other triplet ground-state derivatives of propynylidene have been investigated spectroscopically and they display similarly delocalized electronic structures. − In contrast, singlet ethynylcarbenes (such as 1 ) can best be represented by a localized carbene center in α-position to a localized CC bond …”

Synthesis of (alk-1-ynyl)cyclopropenium salts via the reaction of (alk-1-ynyl)chlorocarbenes with diphenylacetylene

“…1 triple bond of perchlorates 7a-c are downfield (126-138 ppm) with respect to the corresponding signals of other acetylenes, for example, (alk-1-ynyl)halocyclopropanes (75-95 ppm). [4][5] These results suggest the conjugation between the triple bond and the cyclopropenium cation in salts 7a-c. This work was supported in part by the Russian Foundation for Basic Research (grant nos.…”

“…Previously we have discovered a new class of carbenic species, (alk-1-ynyl)halocarbenes, and their ability to add to double bonds of alkenes with the formation of corresponding 1-(alk-1-ynyl)halocyclopropanes. [1][2][3][4][5] At the same time, any data on the ability of these carbenes to react with alkynes are not available. Special interest in these reactions can be explained by the possibility of formation, analogously to halo(phenyl)carbenes, 6 of (alk-1-ynyl)-substituted cyclopropenium salts, previously unknown acetylenic compounds with the conjugation between the carbon-carbon triple bond and the cyclopropenium cation.…”

“…The formation of cyclopropenium salts 7a-c and 9a-c proceeds, according to Scheme 1. (Alk-1-ynyl)halocarbenes [1][2][3][4] 3 generated by the reaction of halides 1a-c or 2 with Bu t OK add to the triple bond of tolan to form chlorides 4a-c, which react with Bu t OK under the reaction conditions with the formation of corresponding isomeric ethers 5a-c and 6a-c. These ethers give (alk-1-ynyl)cyclopropenium perchlorates 7a-c on the treatment with HClO 4 and (2-bromoalk-1-enyl)cyclopropenium bromides 9a-c under the action of HBr.…”

Infrared-Spectroscopic Study of (4-Methylpent-3-en-1-ynyl)methylthiocarbene, Its Photochemical Transformations, and Reactions in an Argon Matrix

“…Carbenesunstable compounds of divalent carbontogether with ions and free radicals are one of the main classes of highly reactive intermediates that determine the direction of chemical reactions and the structure of the resulting products . They have been well known for almost 70 years and have been a subject of numerous chemical and physicochemical studies. − In recent years, considerable attention has been paid to the study of ethynylcarbene- conjugated triplet carbon chain molecules, whose electronic structure and reactivity have been explored by different spectroscopic and computational methods. − These species are of interest due to their unusual electronic structure, as well as their participation as intermediates in many important processes in astronomy , and polymer photochemistry. − Base-induced generation of different alkynylcarbenes and their reactions with various organic substrates have been the subjects of our previous works. − Ten years back, a highly delocalized triplet carbene comprising both vinyl and ethynyl groups at the carbene center, 5-methylhexa-1,2,4-triene-1,3-diyl, was generated in a low-temperature Ar matrix upon UV photolysis of 5-ethynyl-3,3-dimethyl-3 H -pyrazole and studied by IR and ESR spectroscopies. , It was shown that two major photolytic rearrangements of this carbene represent reactions characteristic of vinyl carbenes, resulting in the formation of 1-ethynyl-3,3-dimethylcyclopropene and 3 E -2-methylhexa-1,3-dien-5-yne. A minor reaction, typical of ethynylcarbenes, leads to the formation of singlet 2-(2-methylpropenyl)­cyclopropenylidene.…”