Hydroacylation of 1,3-dienes

Based on Watanabe s intermolecular hydroacylation of olefins with aldehydes,348 Kondo and Misudo developed the first ruthenium-catalyzed hydroacylation of 1,3-dienes with aldehydes (Scheme 71). Usually, palladium-mediated hydroacylations of 1,3-dienes with aldehydes give tetrahydropyran and/or open-chain homoallylic alcohol derivatives.350 However, in the present ruthenium-catalyzed transformations, the corresponding /3,7-unsaturated... 

Later, they also reported an intermolecular hydroacylations of 1,3-dienes with aromatic aldehydes yielding the corresponding j8,y-unsaturated ketones (Eq. 51) [79]. This reaction does not require a CO atmosphere. The addition of formyl C-H bond in formic acid esters and amides to olefins and conjugate... 

The first ruthenium-catalyzed intermolecular hydroacylation of 1,3-dienes with aldehydes via a jt-allylmthenium intermediate has been reported (Eq. 5.36) [60],... 

Ruthenium-catalyzed hydroacylation of 1,3-dienes with aromatic and heteroaromatic aldehydes occurs in relatively good yields to afford the corresponding fi, /-unsaturated ketones . Isoprene and benzaldehyde were treated with 4 mol% Ru(COD)(COT) (COD = 1,5-cyclooctadiene, COT = 1,3,5-cyclooctatriene) and 4 mol% PPhs under argon for 40 hours to give 54% 80 (equation 41). The key intermediate is an acyl- ) -(allyl)ruthenium complex which undergoes reductive elimination to give the corresponding... 

The allylic activation of 1,3-dienes by Ru(COD)(COT) makes possible their hydroacylation to form /5,y-unsaturated ketones via C-H activation of aldehydes at the same metal center [117], and their selective coupling with acrylic compounds [18] (Eq. 87). 

Here catalysis involves the formation of a ruthenium vinylidene, an anti-Markovnikov addition of water (368), and cyclization of an acylmetal species onto the alkene. Although cyclization may occur via hydroacylation (Scheme 52, path A) (460-462) or the Michael addition reaction (Scheme 52, path B) (463,464), the requirement for an electron-withdrawing substiment on the alkene and the absence of aldehyde formation suggest path B to be the more likely mechanism (465,466). Trost discovered that the use of the cationic mthenium catalyst CpRu(MeCN)3+PFg is tolerant of 1,2-di-and trisubstimted alkenes and promotes cyclization of 1,6- and 1,7-enynes to five- and six-membered ring products (467). In a number of examples, the mthenium reaction is complementary to the Pd-catalyzed cyclization described above, selectively forming the 1,4-diene over the traditional 1,... 

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