Methyleneketenes and methylenecarbenes. X. Precursors for the generation of methyleneketene and deuterated methyleneketenes for microwave spectroscopy

Abstract

The synthesis of a mixture of deuterated cyclopentadiene adducts (3) required for the pyrolytic generation of CHD=C=C=O and CD2=C=C=O is described. Methyleneketene is conveniently generated for microwave spectroscopy by flash vacuum pyrolysis of acrylic anhydride at 510- 560°. Pyrolysis of diphenylmethyl propiolate gives benzophenone and methyleneketene (or its decomposition products)as the major process, but minor processes leading to diphenylmethane, fluorene and 3-phenylphthalide also occur.

Rotational Spectra of Unsaturated Carbon Chains Produced by Pyrolysis: The Case of Propadienone, Cyanovinylacetylene, and Allenylacetylene

“…Propadienone is a kinetically unstable compound which has never been isolated in the condensed phase, even when diluted in a solvent. Therefore, it has been produced directly in situ by exploiting the methodology described in the literature, i.e., through gas-phase pyrolysis of acrylic anhydride, , and using the apparatus described in the Experimental Details. Given its relatively high vapor pressure, the precursor (acrylic anhydride) was kept in a water/ice bath at 0 °C to facilitate the flow regulation inside the pyrolysis system.…”

Synthesis and structure-activity relationships of new chiral spiro-β-lactams highly active against HIV-1 and Plasmodium

“…Optical rotations were measured on an Optical Activity AA-5 electrical polarimeter. 6-Diazopenicillanate 4 [14], 6-alkylidenepenicillanates 10 [17] and 16 [16], diazomethane [38], allenoates 11 [39], and 17 [40], and diphenylmethyl propiolate 5d [41] were prepared as described in the literature. Acetylene dicarboxylic acid, propiolates 5a-c, ethyl-2-butynoate (13a), methyl-2-butynoate (13b) and benzyl diazoacetate (22) were purchased and used as such.…”

Flash-Vacuum Pyrolysis of 1,2,4-Triazolides: A New Synthesis of Functionalized Oxazoles

“…Such migrations of carbanylated substituents from nitrogen to carbon have also been observed photochemically and thermally for pyrrole d e r i u a t i~e s~~-~~. Acylated derivatives of pyrazole, like 4, besides a small amount of isomerization15, mainly undergo fragmentation into pyrazole [?I and ketene [6] [16][17][18]. Photalysis of I-acetyl-1,2,4-triazole [?I does not yield any identifiable product19 ; on the contrary, upon FVP conditions, ring transformation into 5-methyloxazole [&I has been described by our laboratory20.…”