Chemistry of .alpha.,.alpha.'-bis(diazo)ketones

Abstract

The synthesis and decomposition of 2,6-bis(diazo)cyclohexanone (1) and 1,3-bis(diazo)-l ,3-diphenylpropan-2-one (4) are reported. Cyclopropenones are established as intermediates in the photolytic decompositions. Thermal decomposition of 4 catalyzed by silver oxide and cuprous chloride also involves formation of 1,3-diphenylcyclopropenone. On the other hand, uncatalyzed thermal decomposition of 4 leads to 2,5-diphenyl-3,4-diazacyclopentadienone whose formation represents a novel electrocyclic ring closure. This fascinating intermediate behaves as both a dienophile with 2,3-dimethyl-l,3-butadiene and a diene with norbornene in cycloadditions. Control experiments associated with the above studies uncovered an unusually facile photodeconjugation of an «,/3-unsaturated ester in which the normal intramolecular pathway is geometrically precluded.

100 Years of the Wolff Rearrangement

“…[289] Minor amounts of β, γ-unsaturated esters and of β-alkoxy esters were also detected. [290] Irradiation of 1,3-diazo-1,3-diphenylpropan-2-one (382), using monochromatic light at 436 nm, resulted in the isolation of diphenylcyclopropenone (379, R ϭ Ph) whereas at shorter wavelengths diphenylacetylene (380, R ϭ Ph) was obtained. [290] Matrix isolation proved to be helpful in elucidating the reaction mechanism.…”

“…[290] Irradiation of 1,3-diazo-1,3-diphenylpropan-2-one (382), using monochromatic light at 436 nm, resulted in the isolation of diphenylcyclopropenone (379, R ϭ Ph) whereas at shorter wavelengths diphenylacetylene (380, R ϭ Ph) was obtained. [290] Matrix isolation proved to be helpful in elucidating the reaction mechanism. Irradiation (Ͼ 274 nm) of 381 in argon at 8 K gave first diazoketene 376 and then cyclopropenone 379 (both with R---R ϭ (CH 2 ) 4 , IR detection).…”

Carbenoid insertions into benzylic C–H bonds with heterogeneous copper catalysts

“…The two diastereomers erythro-8 (like) and threo-8 (unlike) were identified by comparison of their 1 H NMR spectrum with that of the analogous erythro and threo methyl 2,3-diphenyl-3-methoxypropionate, 26 and other related compounds. 27 The higher coupling constant in the CH-CH system (10.4 vs 9.6 Hz) and the higher chemical shift of the methoxy group (3.22 vs 3.07 ppm) are in agreement with the threo configuration.…”

Cycloadditions and other chemistry of 4-oxygenated pyrazoles

“…Hence a four-step radical mechanism for conversion of 20 to 16 is probable but a four-step heterolytic mechanism or a combination of both cannot be ruled out. Trost et al (12) observed the formation of 16 from the bisdiazoketone 27 and proposed a mechanism in which 27 is converted to 1 and further 27 reacts with 2 moles of 1 with elimination of 2 moles of N,. This mechanism may still be correct provided 27 is present but this current work reveals an alternative route which does not require reaction of 27 with 1.…”