Dicarbonyl coupling

Dicarbonyl coupling (8,483). This Ti-catalyzed coupling offers a useful route to cyclic sesquiterpenes such as humulene (4). The precursor is obtained by coupling a vinylic zirconium compound (1) with the u-allylpalladium complex (2) to give, after deprotection, the keto aldehyde 3 in 84% yield. This product couples to humulene as a single isomer in 60% yield. 

McMurry, J. E. 1983. Titanium-induced dicarbonyl-coupling reactions. Accounts Chemical Research 16 405-11. 

Oxo esters undergo an intramolecular dicarbonyl coupling reaction on treatment with a low-valent titanium reagent to form a ketone. This was used in the synthesis of (Z)-7,l0,10-trimethyl-bicyclo[7.2.0]undec-6-en-2-one (4) from ethyl ( )-6-methyl-7-(4,4-dimethyl-2-oxocyclobutyl)-hept-5-enoate,108 Interestingly, the configuration of the isolated C -C double bond in the isolated product is sensitive to the reaction conditions. 

Motherwell and Roberts dicarbonyl coupling reaction19 can be improved by substituting l,2-bis(chlorodimethylsilyl)ethane for TMSC1. The intermediate organozinc carbenoids can be trapped with alkenes to produce cyclopropanes, as exemplified in the intramolecular case in equation 3. 

Agranat, I., Suissa, M. R., Cohen, S., Isaksson, R., Sandstrom, J., Dale, J., and Grace, D. (1987) A novel titanium-induced aromatic dicarbonyl coupling. Synthesis of a chiral strained polynuclear aromatic hydrocarbon, J. Chem. Soc., Chem. Commun., 381-383. 

JCS Chem Comm, (1986), 1665 Review "Titanium Induced Dicarbonyl-Coupling Reactions" McMurry, J.E. Accts Chem Res, (1983), 405... 

Extension of the low-valent titanium dicarbonyl coupling reaction to ketoesters leads to cyclic enol ethers, and hydrolysis of these affords the corresponding cycloalkanones. This methodology has been applied to the synthesis of various natural products, as exemplified by the preparation of the highly unsaturated C(14) macrocyclic ketone shown below. 

In addition to the various dicarbonyl coupling reactions previously described, SmF also promotes the cross-coupling of carbonyl substrates with oximes [45] and aldimines [46], Intermolecular examples have been reported, but mixtures of dia-stereomers result unless the ketone is sterically biased (Eq. 39). Much more useful... 

In the original formulation [81a], DBN and a slight molar excess of AgN03 in MeCN solution were used. Depletion of the starting penicillanic ester was followed by tic and, when complete, obtained silver azetidinyl mercaptides 126 were in situ treated with acyl chlorides to afford thioesters 127 these in turn were oxidized at the butenoate double bond to give lH-4-thioesters 128, key intermediates of Woodward s original phosphorane-thioester cyclization route to penems [1, 48], or ozonized to the iV-oxalo compounds 129, immediate penem precursors by a newly discovered reductive dicarbonyl coupling [82]. 

S. Iwatsuki, M. Kubo, and Y. Itoh, Preparation of poly(3,4-dibutoxy-2,5-thienyl-vinylene) via titanium dicarbonyl-coupling reaction of dibutoxythiophene-2,5-dicarbaldehyde, Chem. Lett. 7995 1085. 

In an octahedral trans dicarbonyl, coupling leads to the spectrum of Fig. 10.8a. The COs may vibrate in phase, in which case they both... 

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