Diazo compounds palladium acetate

Diazo compound 2 is obtained by thermal ring opening of the bicyclic pyrazoline 1." Catalytic decomposition of 2 with copper(I) iodide in refluxing benzene yields the bicyclo[1.1.0]butane 3. The same result is achieved with bis(acetonitrile)palladium(II) chloride as catalyst, whereas rhodium(II) acetate dimer and copper(I) cyanide are unreactive. 

Cyclopropanation reactions with these catalysts are typically carried out with 0.5-2 mol% (with respect to the diazo compound) of catalyst and a five- to tenfold excess of alkene. Under these conditions, the formation of formal carbene dimers [e.g. diethyl ( )-but-2-enedioate and (Z)-but-2-enedioate from ethyl diazo acetate], arising from the competition between alkene and the metal-carbene intermediate for the diazo compound, can be largely suppressed. It has been shown, however, that the control of the addition rate of the diazoacetic ester has no effect on the cyclopropane yield with (dibenzonitrile)palladium(II) chloride as catalyst, in contrast to tetraacetatodirhodium, Rh6(CO)16, and CuCl P(OR)3.152... 

Apart from routine applications to cyclopropane synthesis,the application of new catalysts to the decomposition of diazo-compounds has received considerable attention. The use of palladium acetate, originally reported in 1972 by Paulissen et o/., has been extended and applied to diazomethane and ethyl diazoacetate in the presence of aP-unsaturated carbonyl compounds. With a- and a-substituted aP-unsaturated ketones, stereospecific cis-addition occurs in excellent yields, but the catalyst proves to be ineffective with analogous trisubstituted olefins, as illustrated for the formation of (110) with diazomethane. The use of palladium chloride with the... 

Cyclopropanes and their derivatives are versatile building blocks in organic synthesis. They are also present in many natural products and frequently included as substituents in the structure of new biologically active substances. While cydopropylbo-ranes have long been described [34], it is only since an efficient access to the boronic esters was reported that they really attracted chemist s interest. In 1989, the first additions of carbenes, generated from diazo compounds and palladium acetate, to pina-col alkenylboronic esters were reported to give racemic mixtures of cyclopropyl-boronates (Scheme 9.15) [35]. 

By Cyclopropanation. Alkenes undergo a cyclopropanation reaction with diazo compounds (caution) such as diazomethane or ethyl diazoacetate in the presence of a catalytic amount of palladium acetate. With diazomethane, a selective cyclopropanation of terminal double bonds can be obtained (eq 52). ... 

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