Dicarbonyl coupling reaction

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. 

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... 

Motherwell and Roberts dicarbonyl coupling reaction can be improved by substituting l,2-bis(chlorodimethylsilyl)ethane for TMSCl. The intermediate organozinc carbenoids can be trapped with Series to produce cyclopropanes, as exemplifi in the... 

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. 

The coupling reaction of arenediazonium ions with semidione radicals (12.84, obtainable by reduction of 1,2-diketones, 12.83) is also included here in the discussion of 1,3-dicarbonyl compounds, although it is a coupling with a nucleophilic radical and does not strictly belong in this context. The reaction (Scheme 12-43) was... 

A McMurry coupling reaction involving 3-aza-1,5-dicarbonyl compounds gave 2,5-dihydro-3,4-diarylpyrroles <06SL490>. The latter were converted into the corresponding 3,4-diarylpyrroles by irradiation (Hg lamp, 500 W) in acetonitrile. 

An oxidative coupling reaction of hydroxypyridinones with /5-dicarbonyl compounds leads to the formation of dihydrofuro[3,2- ]pyridinone derivatives (Equation 48) <2005TL5085>. The reaction is carried out as a one-pot synthesis. 

The general process involved in a bis-Wittig coupling reaction (shown in Scheme 11) is the condensation of a bis-Wittig reagent with a suitable dicarbonyl compound (usually a dialdehyde) to produce a ring. The resulting products are normally uniquely accessible by... 

A further general route to the 1,2-dicarbonyl system involves the oxidation of a-ketols (acyloins) (cf. the preparation of benzil from benzoin, Expt 6.143). The acyloins may be prepared from carboxylate esters by a radical coupling reaction involving the use of finely divided sodium metal in anhydrous ether, benzene, or toluene.144... 

Alkenylboron compounds cyclopropanations, 9, 181 haloetherification, 9, 182 hydrogenation and epoxidation, 9, 182 metal-catalyzed reactions, 9, 183 metallic reagent additions, 9, 182 via radical addition reactions, 9, 183 5-Alkenylboron compounds, cross-coupling reactions, 9, 208 Alkenyl complexes with cobalt, 7, 51 with copper, 2, 160, 2, 174 with Cp Re(CO) (alkene)3 , 5, 915-916 with dicarbonyl(cyclopentadienyl)hydridoirons, 6, 175 with gold, 2, 255... 

Fig. 8 Iron-catalyzed coupling reactions of P-dicarbonyl compounds with ethers, sulfides or tertiary amines...

The coupling reaction of a-keto esters with allyl, propargyl, and allenyl halides using indium metal in aqueous solvents affords a-hydroxy-y,<5-unsaturated esters (Equation (28)).197,198 1,3-Dicarbonyl compounds undergo efficient carbonyl allylation reactions in an aqueous medium through a Barbier-type reaction (Equation (29)). The reaction is general and a variety of 1,3-dicarbonyls has been alkylated using allyl bromide or allyl chloride in conjunction with indium.199... 

In 1977, McMurry and Kees [152] developed a titanium-induced intramolecular coupling procedure to form cycloalkenes from dicarbonyl compounds. Mechanistically, as shown in Scheme 85, the coupling reaction proceeds by an initial pinacol dimerization of the dicarbonyl 253 to 254, followed by titanium-induced deoxygenation to afford alkene 255. 

A microwave-assisted three-component coupling reaction of 5-amino-3-phenyl-pyrazole, a cychc 1,3-dicarbonyl compound and an aromatic aldehyde has been described by Chebanov and co-workers [121]. Depending on the apphed reaction conditions a series of 4-aryl-3-phenyl-l,4,6,7,8,9-hexahydro-l// pyrazolo[3,4-h] quinolin-5-ones 80, 9-p-tolyl-6,6-dimethyl-2-phenyl 5,6,7,9-tetrahydro-pyrazolo [5,l-h]quinazolin-8-ones 81, or 4-aryl-5a-hydroxy-4,5,5a,6,7,8-hexahydropyra-zolo[4,3-c]quinolizin-9-ones 82 can be formed (Scheme 61). 

Compared to diazonium salts, diazo compounds are generally much less reactive towards nucleophiles than towards electrophiles. As a result of this azo coupling reactions of diazo compounds are the exception rather than the rule. Electron withdrawing substituents on the diazo carbon increase the reactivity towards nucleophiles. Consequently the ability to undergo azo coupling reactions increases from diazomethane to diazocarbonyl- and 2-diazo-l, 3-dicarbonyl compounds. Among the earliest reactions known were those with cyanide and sulfite ions Tertiary phosphines, as opposed to amines, can form stable addition complexes with diazoalkanes probably due to the ability of phosphorus to stabilize the betaine with its empty d orbitals (6). 

The rates of azo coupling reactions with P-dicarbonyl compounds as a function of pH were also studied by Stjrba s group m,s6,i6o,i67) xheir results are consistent with those of Hashida but cover a smaller range of compounds. 

Hashida et al. also found a good linear relationship for the azo coupling rates of 11 P-dicarbonyl compounds and the pK values of these C-acids. However, two dicarbonyl compounds with a trifluoromethyl group attached to one of the carbonyl functions were exceptions. Furthermore, no relationship between log k and pK could be observed for azo coupling reactions of active methylene compounds other than p-dicarbonyls. 

An alternate approach to these useful 1,3-dicarbonyl substrates may be achieved through enolate orthoester acylation. Titanium enolates have been employed to effect this transformation (eq 19). Similarly, treatment of the titanium enolate of p-ketoimide with dioxolane orthoesters results in the formation of a masked tricarbonyl compound (eq 20). Trimethyl orthoacetate and Triethyl Orthoacetate are not appropriate partners in these coupling reactions. ... 

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