Titanium-induced coupling

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

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... 

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. 

The first total synthesis of ( )-sarcophytol B (5) from S./i-famesal (92), which was reported by McMurry et al. in 1989, used a low-temperature titanium-induced pinacol coupling reaction of 1,14-dialdehyde as the key step. They concluded that the natural sarcophytol B has the stereochemistry of a trans diol (Scheme 6-5). Li et al. reported on a concise total synthesis of ( )-sarcophytol B (5) from /i./i-famesol (91) by a low-valent titanium-mediated intramolecular McMurry... 

Yue et al. reported on the total synthesis of / -(—)-cembrene A by using the mod-ihed Wittig reaction and titanium-induced intramolecular carbonyl coupling as key steps the overall yield is 29% starting from -geranylacetone (164) and R-(+)-limonene (168) (Scheme 6-15). ... 

An alternative strategy to prepare ( )-cembrene A (59) by this group is described below. The key step here is a titanium-induced intramolecular carbonyl coupling reaction starting from -geranylacetone and geraniol (137) (Scheme 6-16). ... 

Dams, R., Malinowski, M., Westdorp, I., Geise, H. On the mechanism of the titanium-induced reductive coupling of ketones to olefins. J. 

Poly(ferrocenylene vinylene) derivatives 68 with values of 3,000-10,000 and polydispersities of ca. 2.2-2.8 (determined by GPG) were synthesized in 1995 in high yields via a titanium-induced McMurry coupling reaction of the corresponding alkylferrocenyl carbaldehyde monomers (Equation (26)). " Gharacterization of these soluble polymers by NMR and IR revealed the presence of trans-Yinylcnc units. The UV-VIS spectra of the polymers are similar to those of the monomers and this indicates a fairly localized electronic structure in the former. The relatively limited electron localization is also reflected in the electrical and optical properties. For example, the values for iodine-doped conductivity a= 10 Scm ) and non-linear third-order optical susceptibility (x = 1-4 x 10 esu) are lower than those of linear conjugated polymers such as poly(l,4-phenylene-vinylene) (a = 2.5x 10 Scm" = 8 X 10 esu). 

Titanium-induced Intramolecular Carbonyl Coupling Reactions... 

Table 9-1 Effect of the ring size on intramolecular, low-valent titanium-induced carbonyl coupling reactions.

Conjugated polyene fragments occur in a wide variety of naturally occurring organic compounds, such as macrolides, carotenoids, and leukotrienes. The synthesis of all-trans triene 734 is readily accomplished by low-valent titanium-induced reductive elimination of l,6-dibenzoate-2,4-diene 733 [210] (Scheme 97). The requisite cis, c/5-diene geometry is obtained by a stereospecific reduction of diyne 731 with activated zinc—copper couple. 

The titanium-induced reductive coupling of 3,4-dibutoxythiophene-2,5-dicarbaldehyde (TiCU, Zn) has given poly (3,4-dibutoxy-2,5-thienylene-vinylene), with good solubility in organic solvents <93CL1085>. 

This reaction was first reported by Furstner in 1991It is a low-valent titanium-induced or -mediated intramolecular reductive alkylidenation of alkyl (or aryl) 2-N-acylamidophenyl ketones to afford 2,3-disubstituted indoles, also known as titanium-induced intramolecular oxoamide coupling or the zipper reaction. Therefore, this reaction is referred to as the Furstner indole synthesis. 

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