Hydroacylation directed

Jim et al. [24] reported the above reaction in an article entitled Chelation-Assisted Intermolecular Hydroacylation Direct Synthesis of Ketone from Aldehyde and 1-Alkene in 1997 [24]. They also reported on the reaction mechanism, as shown in Scheme 7.1 [24]. 

Jun CH, Lee H, Hong JB (1997) Chelation-assisted intermolecular hydroacylation direct synthesis of ketone from aldehyde and 1-aIkene. J Org Chem 62 1200... 

Related oxidation processes have been reported that allow the generation of esters directly from aryl aldehydes [6] and the hydroacylation of a-keto esters with aldehydes [7]. 

A recyclable system for the directed rhodium-catalyzed hydroacylation of olefins was reported using a homogeneous phenol and 4,4 -dipyridyl solvent system at 150 °C. High yields were obtained even after eight cycles and the ketone product was obtained after decantation (Equation (132)).115... 

As already mentioned, Pd - H+ generated at the methanolysis step may transform into Pd-OCH3+ by the action of a quinone. Vice versa, Pd-OCH3+ generated in the protonolysis step may undergo - H elimination with formation of Pd - H+, as it occurs for the hydroacylation of ethene to DEK [33]. Direct shift from the hydride mechanism to the carbomethoxy mechanism has been demonstrated by Iggo et al. [58] (Sect. 3.3.2). 

An interesting example is the hydroiminoacylation reaction, a good alternative to hydroacylation reactions, using aldimines as a synthetic equivalent to aldehydes (Scheme 4) [4]. The rhodium-catalyzed hydroiminoacylation of an olefin with aldimines produced a ketimine which could be further acid-hydrolyzed to give the ketone. The reaction proceeded via the formation of a stable iminoacylrhodi-um(III) hydride (this will be discussed in the mechanism section), production of which is facilitated by initial coordination of the rhodium complex to the pyridine moiety of the aldimine. This hydroiminoacylation procedure opened up the direct... 

The use of a formyl group as a directing functionality is challenging because, in the case of the low-valent transition metal-catalyzed reaction of aldehydes with an olefin, aldehydes are prone to undergo decarbonylation or hydroacylation of the olefins. The following protocol to suppress the decarbonylation, one being steric and the other electronic in nature, can be used. In the case of the reaction of 1-methylin-dole-3-carboxaldehyde with ethylene, the ethylation product is also obtained in quantitative yield (Eq. 9.5) [13]. 

Compared with C—C n and C—N bond formation, there are fewer examples of C—O bond formation reactions via direct sp2 C—H bond activation. Dong and co-workers reported a novel approach to form chiral lactones (Equation 11.42) [81]. This C—H bond functionalization strategy involves an unprecedented Rh-catalyzed hydroacylation of ketones. The basicity of the phosphine ligand plays a critical role in promoting hydroacylation over competitive decarbonylation. 

Scheme 8.22 Substrate-directing intermolecular hydroacylation reaction reported by Dong.

KimJH, Jun CH. Direct hydroacylation of polybutadiene by Wilkinson s complex. Bull Korean Chem Soc. 1999 20 27-29. 

Activation by rhodium complexes has been used to achieve direct exchange of ketone methyl or aryl groups with an aryl group on ArB(OH)2, selective C(CO)-C bond cleavage on reaction of ketones with water, oxidative acylation between secondary benzamides and aryl aldehydes with subsequent intramolecular cyclization to 3-hydroxyisoindolin-l-ones, " cross dehydrogenative coupling to form xanthones from 2-aryloxybenzaldehydes, and activation of the aldehydic C-H bond to achieve hydroacylation of unactivated alkenes by salicylaldehyde derivatives and of vinylsilane by benzaldehyde. ... 

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