2-Diazo-l,3-diketones

Diazo-l,3-diketone ergeben bei der thermischen Reaktion mit Thiocarbonsaure-amiden zu-meist nur niedrige Ausbeuten an 1,3-Thiazolen, weil bevorzugt 4-Oxo-4H-l,3-oxazine gebildet werden1841. 

The Regitz reaction involves the transfer of a diazo group from the tosyl azide or mesyl azide to active methylene compounds such as 1,3-diketones and their derivatives (1) in the presence of a base leading to 2-diazo-l,3-diketones (2). 

This mechanism is, however, difficult to apply to the fast cycloaddition of diazoacetates (Alder et al., 1931) and 3-diazobutane-2-one (Diels and Konig, 1938) with alkenes of the bicyclo[2.2.1]heptene type, because alkene C-atoms without electron-withdrawing substituents show no electrophilic character. The reverse sequence of steps in (6-4), i. e., first an additon of N at the central C-atom of the acrylate, would also be unusual, as the N ()ff)-atom of diazoalkanes is only a weak electrophilic center. Fleischmann (in Huisgen s group, 1958) showed that, in such cyclization reactions, the rate of reaction of diazomethane with bicyclic alkenes relative to that of )ff-diazo ketones and 2-diazo-l,3-diketones is higer by a factor of 10" -10. ... 

Ring contraction of 2-diazo-l,3-diketones 2-Azetidinones from 3-diazo-2,4-pyrrolidiones... 

Presset M, Coquerel Y, Rodriguez J. Microwaves-assisted Wolff rearrangement of cyclic 2-diazo-l,3-diketones an eco-compatible route to a-carbonylated cycloalkanones. J. Org. Chem. 2009 74 415-418. 

The microwave-assisted Wolff rearrangement of cyclic 2-diazo-l, 3-diketones in the presence of aldehydes and primary amines provides a straightforward access to... 

The microwave-assisted Wolff rearrangement of cyclic 2-diazo-l,3-diketones was performed in the presence of a stoichiometric amount of alcohol, amine, or thiol (Presset et al., 2009b). It is an efficient, and environmentally friendly synthetic protocol for the synthesis of a-earbonylated cycloalkanones. This approach proves superior to existing protocols in scope and ecocompatibility. 

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