2-butyne Research Articles

ChemInform Abstract: Amidochlorination of Vinylacetylene.

AbstractN,N‐Dichloroethylurethane (II) is coupled with vinylacetylene (I) to give a 1:2 mixture of the allenyl (III) and the butynyl carbamate (IV).

Gas phase synthesis of selenophene from dimethyl selenides and acetylene

Gas phase synthesis of selenophene from dimethyl selenides and acetylene

Cycloaddition reactions of 3-vinylthiophen

Cycloaddition reactions between 3-vinylthiophen and the dienophiles maleic anhydride, methyl acrylate, dimethyl acetylene - dicarboxylate, and methyl propiolate give products including methyl benzo[b]thiophen-7-carboxylate (11) and its dihydroderivative (10), the 6,7-dicarboxylic acid (3), its dimethyl ester (7) and dihydroester (6); the naphtho[a,b]dithiophen (14), and the novel ethano bridged benzo[b]thiophen (15).

Dimeric 1,4‐Dichloro‐2,3,5,6‐tetramethyl‐1,4‐dialumina‐2,5‐cyclohexadiene, a Compound with Aluminum‐Olefin π‐Bonds

The low-temperature reaction of the “high-temperature” molecule AICI—the first preparative application of an Al subhalide—with CH3CCCH3 gives the title compound 1. The monomers of this air- and moisture-sensitive compound are twisted by 90° with respect to each other. The dimer is held together by four Al-olefin π bonds. Such compounds were previously unknown.

Disproportionation of norbornene derivatives

1. The thermal disproportionation of the diene adducts of cyclopentadiene with vinyl acetate, allyl acetate, allyl alcohol, and acetylene has been observed. 2. A two-step scheme is proposed, the limiting step of which is retrodiene decomposition of the starting compounds.

Amidochlorination of vinylacetylene

Amidochlorination of vinylacetylene by N,N-dichlorourethan proceeds by two pathways with the formation-of predominantly acetylenyl (but also allenyl) chlorocarbamates.

Pyrolysis of 2‐methylbut‐1‐ene‐3‐yne between 375 and 450°c

AbstractThe pyrolysis of 2‐methylbut‐1‐ene‐3‐yne (C5H6) has been studied from 375 to 450°C in a quartz reaction vessel in the absence and presence of O2 or NO. From 375 to 425°C, the rates of disappearance of reactant and of formation of dimers are second order in C5H6. The major product is polymer, with the dimers accounting for about 3% of the C5H6 consumed. In addition, toluene and p‐xylene are produced, their production coming, at least in part, from decomposition of the C5H6 dimers (C10H12). Also, trace amounts of CH4, C2H4, C2H6, are formed. The rate coefficients for C5H6 removal and C10H12 formation in the absence of O2 or NO are where the uncertainties are one standard deviation. The reaction mechanism for dimer formation is analogous to that in vinyl acetylene (C4H4) pyrolysis (5), except that in the C4H4 system cyclooctatetraene is seen as an unstable product that isomerizes to styrene, whereas in the C5H6 system, the dimethylcyclooctatetraene apparently is too unstable to be detected. The dimers detected were 2,6‐dimethylstyrene (P4), p‐isopropenyltoluene (P5), and two other unidentified dimers (P3) with nearly identical gas chromatographic retention times. From the effect of the radical scavengers and by comparison of the C4H4 and C5H6 systems, the following mechanistic characteristics were determined: (1) The direct formation of styrene in the C4H4 system comes from a head‐to‐head modified Diels‐Alder six‐member cycloaddition that proceeds through a diradical intermediate. (2) There is no positive evidence for a direct head‐to‐tail modified Diels‐Alder six‐member cycloaddition. However, if it does occur, it does not involve diradicals but must be concerted. (3) Cyclooctatetraene is formed in concerted, non‐free‐radical mechanisms that may proceed both by head‐to‐head and head‐to‐tail eight‐member cycloadditions. For the C5H6 system, the head‐to‐head adduct isomerizes to P3, whereas the head‐to‐tail adduct isomerizes to P3, P4, and/or P5. and/or P5. Kinetic data suggest that P3 is not produced from the cyclooctatetraene intermediate, in which case, head‐to‐head addition would not occur. It appears that the head‐to‐head additions are free radical in nature and proceed mainly through a six‐membered ring intermediate, while head‐to‐tail additions are a concerted molecular process and proceed mainly through an eight‐membered ring intermediate.

Total synthesis of steroids. Part 2. Preparation of C-10 methylated steroids. Regio- and stereocontrol in a diene addition to methyl Z-2-methyl-4-oxo-2-pentenoate

A twelve-step total synthesis of 14-epi-androsta-4,9(11),15-triene-3,17-dione from methyl vinyl ketone, 2-methylcyclo-hexane-1,3-dione, acetylene, and methyl Z-2-methyl-4-oxo-2-pentenoate is described. Crucial steps include a stereo- and regio-selective diene addition, an efficient formation of ring D by C-acylation of an acetyl group, and a selective bromine substitution at C-15 in a 15,17-dione intermediate. The stereo- and regioselectivity of the diene addition is generalized for certain other bifunctional aliphatic dienophiles.

Millimeter-Wave Spectrum of Ethyl Acetylene Centrifugal Distortion, Coriolis Interaction and Internal Rotation

The rotational spectrum of ethyl acetylene has been investigated between 70 and 320 GHz. A Coriolis interaction has been found between the first excited state of the methyl torsion and the C - C = C in plane deformation. Splittings of transitions in the first excited torsional state show that the barrier hindering internal rotation of the methyl group amounts to 3271 cal/mole.

Singlet cyclobutyne: a relative minimum on the C4H4 potential-energy hypersurface?

The lowest singlet and triplet electronic states of cyclobutyne have been investigated by using the nonempirical molecular electronic structure theory. Initially, singlet cyclobutyne was studied with use of two-configuration self-consistent-field (TCSCF) methods and triplet cyclobutyne with single-configuration SCF theory. Three standard basis sets, of double-xi (DZ) through double-xi plus polarization (DZ + P) caliber, were employed, the largest being designated C(9s5p1d/4s2p1d), H(4s1p/2s1p). Geometrical structures and harmonic vibrational frequencies were determined with use of analytic gradient techniques. From purely geometrical considerations, the short carbon-carbon bond in singlet cyclobutyne may be labeled a weak (or long) triple bond, with r/sub e/(C double bond C) = 1.258 A. For triplet cyclobutyne a much longer carbon-carbon distance (1.323 A) is predicted, consistent with the sort of C double bond C double bond expected for this diradical species. The triple-bond CC harmonic stretching frequency for singlet cyclobutyne is predicted to be 1911 cm/sup -1/, while the analoguous stretching frequency for the triplet diradical species is 1779 cm/sup -1/. Vibrational analyses demonstrate that (at the levels of theory considered) both singlet and triplet cyclobutyne are relative minima on the C/sub 4/H/sub 4/ potential-energy hypersurface. For the former, the lowest frequency predicted at the DZ+d TCSCF levelmore » of theory is 276 cm/sup -1/, corresponding to the ring-puckering mode. These remarks notwithstanding, it is to be emphasized that singlet cyclobutyne is a highly energetic species, predicted to lie approx. 78 kcal above vinyl acetylene, HC double bond C - CH double bond CH/sub 2/, the absolute minimum among C/sub 4/H/sub 4/ molecules. Finally, singlet cyclobutyne is predicted to lie 13 kcal below its triplet diradical.« less

Reaction of 2-picolyllithium and 6-methyl-2-picolyllithium with vinyl(tert-butyl)acetylene

The possibility of obtaining pyridylallene hydrocarbons with normal structure with a branched grouping in the side chain on the basis of vinyl(alkyl)acetylene hydrocarbons with iso structures and, respectively, 2-picolyl- and 2,6-lutidyllithium is demonstrated.

Destruction of cytochrome P-450 by vinyl fluoride, fluroxene, and acetylene. Evidence for a radical intermediate in olefin oxidation.

Vinyl fluoride, vinyl bromide, fluroxene (2,2,2-trifluoroethyl vinyl ether), and acetylene alkylate the prosthetic heme group of cytochrome P-450 enzymes which catalyze their metabolism. The alkylated heme moiety has been identified in all four cases, after carboxyl group methylation and demetalation, as the dimethyl easier of N-(2-oxoethyl)protoporphyrin IX. The dimethyl acetal derivative of the aldehyde group in this structure is also isolated. The formation of the same prosthetic heme adduct with the four substrates requires introduction of an oxygen at the trifluoroethoxy or halide-substituted terminus of the pi bond and reaction of the unsubstituted terminus with a heme nitrogen atom. This reaction orientation is consistent with a radical intermediate, possibly formed by way of an initial pi-bond radical cation, but is difficult to reconcile with a cationic intermediate. The occurrence of a radical intermediate in the oxidation of olefins by cytochrome P-450 is thus suggested.

Non-terpenoid C-15 metabolites from the red seaweed Laurencia pinnatifida

The structures of absolute configurations of the halogenated vinyl acetylenes which are natural products from the red alga Laurencia pinnatifica (Gmal. Lamour) are described. The structure of trans- pinnatifidenyne 2 was determined by spectral, chemical and X-ray diffraction analyses. The structure of cis-pinnatifidenyne 1 is based on spectral comparison and chemical interconversion with the trans-isomer 2. The structure of the acyclic trienyne 8 was secured as: (6 R,7 R)-3- cis, 9- cis,12- cis,6-acetoxy,7-chloropentadeca-3,9,12-trien-1-yne by synthesis from cis-pinnatifidenyne 1. The reactivity of these compounds to various conditions of catalytic hydrogenation has been examined in detail.

ChemInform Abstract: SYNTHESIS OF HETEROCYCLES BASED ON VINYL ACETYLENES OR DIACETYLENES AND NITROGEN‐CONTAINING BINUCLEOPHILES

Chemischer InformationsdienstVolume 12, Issue 47 Reviews ChemInform Abstract: SYNTHESIS OF HETEROCYCLES BASED ON VINYL ACETYLENES OR DIACETYLENES AND NITROGEN-CONTAINING BINUCLEOPHILES I. A. MARETINA, I. A. MARETINASearch for more papers by this authorA. E. TSIL'KO, A. E. TSIL'KOSearch for more papers by this authorYU. A. ZAICHENKO, YU. A. ZAICHENKOSearch for more papers by this author I. A. MARETINA, I. A. MARETINASearch for more papers by this authorA. E. TSIL'KO, A. E. TSIL'KOSearch for more papers by this authorYU. A. ZAICHENKO, YU. A. ZAICHENKOSearch for more papers by this author First published: November 24, 1981 https://doi.org/10.1002/chin.198147337AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume12, Issue47November 24, 1981 RelatedInformation

The gas-phase chemistry of C 4H 4+−

Ion/molecule reactions, unimolecular dissociations and collisional activation spectra of the C 4H 4 +−, cation have been studied to obtain information about the chemistry, and possibly structure (or structures), of this ion. Precursor molecules employed included 1-buten-3-yne (vinyl acetylene), pyridine, benzene and 1,5-hexadiyne. Some ion reactions involving neutral 1-buten-3-yne were also followed. The reactivity of C 4H 4 +− formed by ionization of neutral C 4H 4 was observed to be the same as that of C 4H 4 +− cations formed as fragments following dissociative ionization.

The reaction of F atoms with C 2H 4. Vibrational Spectrum of the C 2H 4F Intermediate trapped in solid argon

When the products of the reaction between F atoms produced in a microwave discharge and C 2H 4 are frozen in a large excess of argon at 14 K, new infrared absorptions appear which can be assigned to the 2-fluoroethyl radical. Studies of the dependence of the product distribution on the F-atom concentration have confirmed that the stabilization of C 2H 4F 2 plays only a minor role under the sampling conditions typical of these experiments. Isotopic substitution experiments have demonstrated that the steric configuration about the CH bond is randomized as a result of the F-atom reaction. Upon irradiation of the sample with the full light of a medium-pressure mercury arc, absorptions of vinyl fluoride and acetylene and of the acetylene—HF complex grow in intensity, while those of FCD 2CH 2 and of FCH 2CD 2 diminish in intensity and those of FCH 2CH 2 a nd of FCH 2CD 2 are unchanged. The F-atom reactions and photolysis processes which occur in these experiments are discussed, and a tunnelling mechanism is proposed to explain the isotopic selectivity in the 2-fluoroethyl photodecomposition. The vibrational spectrum of FCH 2CH 2 is compared with that derived in a recent ab initio calculation.

Reactions of Pyridylnitrilimines with Dimethyl Acetylene Dicarboxylate

Reactions of Pyridylnitrilimines with Dimethyl Acetylene Dicarboxylate

Rebreathing techniques for pulmonary capillary blood flow and tissue volume.

The variability of three methods of calculating pulmonary capillary blood flow (Qc) and pulmonary tissue plus capillary blood volume (Vt) during rebreathing was assessed in normal humans by using as markers acetylene, ethyl iodide, and dimethyl ether. The methods of analysis were as follows. Method I, the timing of the disappearance curves of the soluble gases was corrected by assuming that the C18O-disappearance curve intercepted at unity at time O. Method II, it was assumed that the acetylene Qc calculated by method I was correct; ethyl iodide and dimethyl ether Vt were solved by an equation using the disappearance slopes of these gases and the acetylene Qc value, thereby avoiding dependence on extrapolated intercept values. Method III, Vt was calculated by solving for a unique value of Qc between pairs of disappearance slopes of acetylene and dimethyl ether, acetylene and ethyl iodide, and ethyl iodide and dimethyl ether. Among the three methods, method I gave the most reproducible values for Vt as determined with acetylene or dimethyl ether. Using method I, both acetylene and dimethyl ether were equally acceptable gases for measurement of Vt; acetylene was a better marker for Qc measurements.

The rhodophytin and chondriol natural products; structures of several new acetylenes from laurencia, and a reassignment of structure for cis-rhodophytin

The structures of five new halogenated vinyl acetylenes are described which are natural products from various species of the red seaweed Laurencia. The structure of epoxyrhodophytin ( 1) was determined by spectral, chemical, and X-ray diffraction analyses. The structures of trans-rhodophytin ( 5) and trans-chondriol ( 8) are based on chemical and spectral comparisons with the previously reported compounds cis-rhodophytin ( 4) and cis-chondriol ( 7). The structures of cis-chondrin ( 14) and trans-chondrin ( 15) were secured by synthesis from cis- and trans-chondriol, respectively. The reactivity of these enol-ethers to various conditions of catalytic hydrogenation has been examined in detail. Hydrogenation yields an unexpected and facile incorporation of oxygen into the reaction products. Based upon these studies, and upon combustion analysis, the structure of rhodophytin has been revised as the vinyl ether rather than the vinyl peroxide originally proposed.

Three new vinyl acetylenes from the marine red alga laurencia

The structures of three new halogenated vinyl acetylenes are described which are natural products from various species of the red seaweed Laurencia. The structure of chlorofucin ( 1) isolated from Laurencia snyderae was determined by X-ray diffraction analysis. Poiteol ( 2) was isolated from Laurencia poitei and its structure was also determined by single crystal X-ray diffraction experiments. The structure of obtusenyne ( 3) was based on a combination of chemical and spectral methods. The 13C NMR spectra of these new compounds are presented and assignments made.