Ketene chemistry carbonylation reactions

Norrish Type I fission of the side chain carbonyl group again at C-4. - Laser flash irradiation has been used as a aethod for the production of n-butylkotene from cyclohexanone. The chemistry of this ketene was studied in detail. The cyclohexanones (9a) undergo both Norrish Type I and II processes on irradiation. The fluorinated compounds (9b) showed a preference for Norrish Type II behaviour. Within the Norrish Type II biradical fluorine substitution leads to a preference for cyclization rather than cleavage. The Norrish Type I biradical afforded a ketene rather than an alkenal. A study of the photochemical reactivity of the diones (10) has shown that both Norrish Typo I and Type II reactivity can take place. The Typo I Type II product ratio is dependent upon ring size. Thus dione (10a) affords the Type II products (11) and (12) while dione (10c) yields the Norrish type I products (I3c-15c) and low yields of the Norrish Type II products (11) and (12). Compound (10b) is intermediate between these results affording a Type I Type II ratio of 0.3. A mechanistic study of the reactions was carried out. - ... 

Looking carefully at the current literature we have learned that the ketene dithioacetal chemistry, widely used for one-carbon homologation of carbonyl compounds, has never been utilized for the construction of ulosonic acids [129]. Besides, ketene dithioacetals, readily available from ketones and aldehydes via the reaction with the ylides generated from substituted dithioacetals in the Peterson, Wittig or Homer-Emmons olefmation, have never been synthesized from lactones. 

The photoinduced Wolff rearrangement of 5-diazo-2,2-dimethyl-l,3-dioxan-4,6-dione has also been examined by TRIR methods [116], These ultrafast measurements, conducted in a PMMA matrix, revealed that the formation of the ketene rearrangement product was complete within 20 ps a carbonyl carbene was not detected in this study. Other applications of TRIR spectroscopy to the study of carbene-related chemistry include investigations of diazirine to diazo rearrangements [117] and of oxygen and sulfur atom transfer reactions [118]. 

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