Wolff rearrangement retro

Nguyen, T. M., Hajnal, M. R., Vanquickenborne, L. G. Theoretical evidence of a singlet a-oxocarbene intermediate in the retro-Wolff rearrangement of azafulvenone. J. Chem. Soc., Perkin Trans, 2 1994, 169-170. 

Also, 2-siloxetenes serve as thermal precursors to silanones. The gas-phase pyrolysis of bis(dimethylsilyl)ketene or (trimethylsilyl)(dimethylsilyl)ketene has been proposed to proceed by a retro-Wolff rearrangement followed by a 1,2-hydrogen shift and electro-cyclic closure to a 2-siloxetene, which then fragments to dimethylsilanone and an acetylene (equation 192)231. 

Recently, other photochemical and thermal retro-Wolff rearrangements have been examined by several researchers.52 55 Under flash vacuum and pulsed pyrolysis conditions, Wentrup and co-workers observed the formation of (cyanovinyl)ketenes from aza fulvenones. Additionally, Moore and co-workers have done extensive work on the gas-phase photochemistry and molecular dynamics on the C2H2O surface using state-resolved spectroscopic methods. 

Barton, T.J. and Groh, B.L., Thermal Extrusion of Dimethylsilanone from (Hydridosilyl)Ketenes. A Retro-Wolff Rearrangement, /. Am. Chem. Soc., 107, 7221,1985. 

Diazoketone 78, under FVP conditions, undergoes a loss of nitrogen and Wolff rearrangement to the corresponding ketene (225) which subsequently undergoes loss of furan via retro Diels-Alder reaction and yields the desired propadienone (226).29 Diazoketone 78 sublimes through a tube heated to 430 °C at 10 4 Torr and the... 

A plethora of products is obtained when either elemol (273), in the presence of p-nitrobenzoic acid (or benzoic acid), or elemyl-p-nitrobenzoate is pyrolysed at about 200 °C. These include the elemenes (274)—(276) together with the selinenes (277)—(281). The sequence of formation and the factors affecting the thermolyses are discussed in depth, together with the data for the thermolysis of dihydro-geijerene (282). This latter compound has been synthesized from germacrone (227) by a Cope rearrangement to j3-elemenone (283) followed by a retro-aldoliza-tion to (284) and subsequent Wolff-Kishner reduction. 

---