Carbenes diazopyruvates

The reaction, formally speaking a [3 + 2] cycloaddition between the aldehyde and a ketocarbene, resembles the dihydrofuran formation from 57 a or similar a-diazoketones and alkenes (see Sect. 2.3.1). For that reaction type, 2-diazo-l,3-dicarbonyl compounds and ethyl diazopyruvate 56 were found to be suited equally well. This similarity pertains also to the reactivity towards carbonyl functions 1,3-dioxole-4-carboxylates are also obtained by copper chelate catalyzed decomposition of 56 in the presence of aliphatic and aromatic aldehydes as well as enolizable ketones 276). No such products were reported for the catalyzed decomposition of ethyl diazoacetate in the presence of the same ketones 271,272). The reasons for the different reactivity of ethoxycarbonylcarbene and a-ketocarbenes (or the respective metal carbenes) have only been speculated upon so far 276). 

Oxepin 404 was prepared by the reaction of ethyl diazopyruvate with 1,3-butadiene in 26% yield. The reaction involves a carbene addition to the double bond with formation of a mixture of cis- and trans-2-oxo-2-(2-... 

Within the framework of the above methodology, 2-methylenedioxole 554 is accessible by trapping a carbene with ketene 555 (77JOM155). Ethyl diazoacetate reacts with substituted cyclohexanones in the presence of Cu(acac)2 in a similar manner to produce spirodioxoles 556 (80JHC721), while the reaction of ethyl diazopyruvate with ketone 557 furnishes the 1 2 adduct 558 [88CI(L)631],... 

---