Conversion of 1,3-Dicarbonyls to 1,4-Dicarbonyls

Photocatalytic Reaction of Diazo Compounds with Aldehydes

“…Kuehne and King reported that treatment of the preformed enamines with diazomethane in the presence of CuCl led to cyclopropylamines which after thermal hydrolysis gave alkylated carbonyl compounds as a mixture of regioisomeric products 45. It was reported that in the presence of Rh(II) complex the reaction of α‐diazo ketones with vinyl ethers afforded cyclopropane derivatives which underwent ring‐opening leading to 1,4‐diketones 46. Such cyclopropanes bearing both electron‐donating and electron‐withdrawing groups were found to be easily cleaved 45–49.…”

“…[45] It was reported that in the presence of Rh(II) complex the reaction of a-diazo ketones with vinyl ethers affordedc yclopropane derivatives which underwent ring-opening leading to 1,4-diketones. [46] Such cyclopropanes bearing bothe lectron-donating and electron-withdrawing groups were found to be easily cleaved. [45][46][47][48][49] We have prepared acyclopropylamine derivative using areported methodology and subjected it to the developed reaction conditions (Scheme 4).…”

Catalyst‐Dependent Chemoselective Formal Insertion of Diazo Compounds into C−C or C−H Bonds of 1,3‐Dicarbonyl Compounds

“…In the case of the silvercatalyzed C( = O) À Cinsertion, 1,3-diketone 2 is first converted by AgOTf into silver enolate A,w hich engages with diazo compound 1 to give the electrophilic silver carbenoid B following loss of molecular nitrogen. Thecyclopropanation of B leads to intermediate C, [24] which then undergoes ar etroaldol fragmentation to afford intermediate D. [25] Upon protonation by HOTf, D releases the 1,4-diketone product 3,with concomitant regeneration of the silver catalyst. In contrast to existing catalytic methods for the insertion of nucleophilic diazo compounds into ketones, [4] thetransient formation of an electrophilic silver carbenoid (B)a nd the subsequent cyclopropanation would represent an ovel mode of carbenoid reactivity.Notably,the formation of product 3ah (Scheme 1) would be consistent with such am echanism, where cyclopropanation occurs at the double bond of the predominant enol form (i.e., that of the methyl ketone), rather than ap athway that relies on migrating group ability,i nw hich migration of the C2 carbon atom would likely be disfavored.…”

Catalyst‐Dependent Chemoselective Formal Insertion of Diazo Compounds into C−C or C−H Bonds of 1,3‐Dicarbonyl Compounds

“…In the case of the silver‐catalyzed C(=O)−C insertion, 1,3‐diketone 2 is first converted by AgOTf into silver enolate A , which engages with diazo compound 1 to give the electrophilic silver carbenoid B following loss of molecular nitrogen. The cyclopropanation of B leads to intermediate C , which then undergoes a retro‐aldol fragmentation to afford intermediate D . Upon protonation by HOTf, D releases the 1,4‐diketone product 3 , with concomitant regeneration of the silver catalyst.…”