Wolff rearrangement vinylogous

Products of a so-called vinylogous Wolff rearrangement (see Sect. 9) rather than products of intramolecular cyclopropanation are generally obtained from P,y-unsaturated diazoketones I93), the formation of tricyclo[2,1.0.02 5]pentan-3-ones from 2-diazo-l-(cyclopropene-3-yl)-l-ethanones being a notable exception (see Table 10 and reference 12)). The use of Cu(OTf), does not change this situation for diazoketone 185 in the presence of an alcoholl93). With Cu(OTf)2 in nitromethane, on the other hand, A3-hydrinden-2-one 186 is formed 160). As 186 also results from the BF3 Et20-catalyzed reaction in similar yield, proton catalysis in the Cu(OTf)2-catalyzed reaction cannot be excluded, but electrophilic attack of the metal carbene on the double bond (Scheme 26) is also possible. That Rh2(OAc)4 is less efficient for the production of 186, would support the latter explanation, as the rhodium carbenes rank as less electrophilic than copper carbenes. 

With 0,-y-unsaturated a -diazo ketones, the resulting [2.1.0]-bicyclic systems (40) were quite unstable and underwent a [2 + 2] cycloreversion to generate ketenes (41), which were then trapped by nucleophiles (Scheme 7). The overall scheme has been named a vinylogous Wolff rearrangement and offers a novel entry to products usually derived from a Claisen rearrangement.102 A recent report describes its application for functionalized angular alkylation in fused ring systems.103 In contrast, the intramolecular re-... 

Both V and VII are highly unstable species, as is copper carbenoid IV. It is conceivable that both evolutionary alternatives follow downhill energy profiles. Whatever the particular mechanism, the transformation of I into II has been termed the vinylogous Wolff rearrangement, since it was taken as a homolog of the classical Wolff transposition. 

Smith, A. B., III. Vinylogous Wolff rearrangement. Copper sulfate-catalyzed decomposition of unsaturated diazomethyl ketones. J. Chem. Soc., Chem. Common. 1974, 695-696. 

Motallebi, S., Mueller, P. The vinylogous Wolff rearrangement catalyzed with rhodium(ll) complexes. Chimia 1992, 46,119-122. 

Ceccherelli, P., Curini, M., Marcotullio, M. C., Rosati, O. Dirhodium tetraacetate-catalyzed decomposition of 3,Y-unsaturated diazo ketones a new entry to vinylogous Wolff rearrangement. Gazz. Chim. Ital. 1994,124,177-179. 

In a recent application, the vinylogous Wolff rearrangement has been used to provide angular functionalization in annelated polycyclic systems (e.g. equation 36). ... 

An efficient total synthesis of ( )-mayurone (197), ( )-thujopsene (187), and ( )-thujopsadiene (198) has been accomplished by a route in which diazoketones (191), (193), and (195) were subjected respectively to vinylogous Wolff rearrangement, photochemical Wolff rearrangement, and a known copper-catalysed intramolecular cyclopropanation reaction (Scheme 18). 

Angularly functionalized polycyclic systems may be prepared from /3,)/-unsaturated diazo ketones by a vinylogous Wolff rearrangement in the presence of coppCT(II) triflate. Dry copper(II) acetylacetonate is equally suitable. 

Cupric sulfate Vinylogous Wolff rearrangement y,d- thylenecarboxylic acid esters from a -diazo-j, 7-ethyleneketones... 

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