Ruthenium-catalyzed cyclocarbonylation

Ruthenium-catalyzed cyclocarbonylation of unsaturated alcohols gives seven-membered lactones in good yields (Equation 6), both ester C-O and C-C bonds being formed <2001TL5459>. 

Starting from the same substrates, even hydroquinones can be prepared by insertion of two molecules of CO. In 1998, Mitsudo and coworkers [21a] demonstrated that hydroquinones could be achieved in a ruthenium-catalyzed cyclocarbonylation by using alkynes and 2-norbornenes. UnsymmetricaUy substituted hydroquinones were obtained in high yields by this novel ruthenium-catalyzed transformation. For the preparation of higher substituted hydroquinones, functionalized alkenes could... 

Hasegawa N, Shibata K, Charra V, Inoue S, Fukumoto Y, Chatani N (2013) Ruthenium-catalyzed cyclocarbonylation of aliphatic amides through the regioselective activatimi of unactivated C(sp3)-H bonds. Tetrahedron 69(22) 4466-4472... 

Murai and coworkers showed a ruthenium-catalyzed cyclocarbonylation of yne-aldehydes in 1998 (Eq. (7.16)) [22]. In the presence of a catalytic amount of Ru3(CO)j2> the reaction of yne-aldehyde with CO (10 atm) in toluene at 160 °C gave a series of a, -unsaturated bicyclic y-butenoUdes in high yields. It is noteworthy that polyfunctional compounds could be formed in a single step by employing this method. 

Scheme 7.6 Proposed mechanism for ruthenium-catalyzed cyclocarbonylation of yne-aldehydes.

The catalytic cyclocarbonylations of diynes proceed efficiently to afford fused cyclohexadienes via trapping of the ruthenacyclopentadiene intermediate by an alkene component <2000JA4310>. Thus, the ruthenium-catalyzed cyclo-co-trimerization of 1,6-heptadiyne derivatives possessing a heteroatom at the 4-position affords heterotricycles in good yields (Equation 110). 

Substituted 2(5ff)-furanones were also synthesized from allenyl alcohols 36 (Eq. 18) [28]. In the presence of 1 mol % of Ru3(CO)12, Et3N and 10 atm CO, 36 underwent cyclocarbonylation to afford the butenolides 37 in excellent yields. Remarkably, the ruthenium(0)-catalyzed cyclocarbonylation protocol is applicable to the syntheses of 6-8-membered a,/ -unsaturated lactones 38-40 in good yields (Eq. 19) [28,29]. 

Similarly, ruthenium(0)-catalyzed cyclocarbonylation of allenic sulfonamides 41 yielded y- and <5-unsaturated lactams 42 (Eq. 20) [30]. The lactam formation is claimed to start with the oxidative addition of a Ru(CO)4 fragment into the N-H bond of 41. Subsequent syn addition of the resultant Ru-H species to the... 

The group of Murai [14] could demonstrate that ruthenium-catalyzed cyclocar-bonylation of yne-imines resulted in formation of lactams (Scheme 1.4a). Catalytic amounts of Ru3(CO)j2 promote this cyclocarbonylation of 1,6- and 1,7-yne-imines, giving bicychc a,fi-unsaturated lactams. Similar to the Pauson-Khand reaction, the... 

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