Ketone-olefin coupling reactions

For additional examples of ketone/olefin coupling reactions promoted by Sml2, see ... 

Matsuda et al. have studied the hydroxyl group directed intermolecular ketone-olefin coupling reactions, induced by Sml2, between a-hydroxy ketones and a,P-unsaturated esters or nitriles (Scheme 30). It was noted that reactions... 

The ruthenium-catalyzed addition of C-H bonds in aromatic ketones to olefins can be applied to a variety of ketones, for example acetophenones, naphthyl ketones, and heteroaromatic ketones. Representative examples are shown in the Table 1. Terminal olefins such as vinylsilanes, allylsilanes, styrenes, tert-butylethy-lene, and 1-hexene are applicable to this C-H/olefin coupling reaction. Some internal olefins, for example cyclopentene and norbornene are effective in this alkylation. The reaction of 2-acetonaphthone 1 provides the 1-alkylation product 2 selectively. Alkylations of heteroaromatic ketones such as acyl thiophenes 3, acyl furans, and acyl pyrroles proceed with high yields. In the reaction of di- and tri-substitued aromatic ketones such as 4, which have two different ortho positions, C-C bond formation occurs at the less congested ortho position. Interestingly, in the reaction of m-methoxy- and m-fluoroacetophenones C-C bond formation occurs at the congested ortho position (2 -position). 

The relationship between the structure and the reactivity of the ketones has been studied [4cj. When 3-acetylthiophene was used in the coupling reaction, the alkylation took place only at 2-position (Eq. 9.2). In the cases of reactions of the ketones, shown in Scheme 9.1, no coupling product was obtained. Based on these results, Murai proposed that the a,/3-conjugate enone framework is important in the C-H/ olefin coupling reaction. 

An intramolecular C-H/olefin coupling reaction can provide a cyclization product. Rhodium complexes involving [RhCl(coe)2]2-PR3 and ( -C5Me5)Rh(C2H3SiMe3)2 complexes are superior as catalysts. Some ruthenium complexes are also reasonably effective for cyclization reactions. Intramolecular olefmic C-H/olefm coupling with the aid of Ru(CO)2(PPh3)3, which is also effective for the reaction of aromatic ketones with olefins, yields the carbocyclic compounds in high yield (Eq. 9.11) [25]. 

In 1996, the present authors extended their C-H/olefin coupling to the C-H/ CO/olefin coupling reaction [40]. Carbonylation of imidazole derivatives takes place in the presence of Ru3(CO)12 as the catalyst. The C-C bond formation occurs at the 4-position (Eq. 26). In these reactions, the linear ketones are the major products. Various functional groups, e.g., nitrile acetal, and ether, are tolerant. 

An analogous ruthenium dihydride complex. RuH2(CO)(PPh3)3, has recently attracted much attention because of its ability to catalyze olefin coupling reactions of aromatic ketones via C—H bond activation (eq (46)) [152]. 

Figure 10.4 A possible intermediate in the olefin coupling reaction of aromatic ketone catalyzed by RuH2(CO)(PPh3)3. Other ligands are omitted.

Ketyls generated by the reaction of SmE with aldehydes and ketones have been incorporated into numerous sequential processes in which a radical reaction is involved. Sequential radical processes, radical cyclization/carbonyl additions, radical cyclization/substitution reactions, nucleophilic acyl substitution/radical cyclizations, cyclization/elimination processes, and others have all been realized. Because these types of reactions have been extensively reviewed [2b, 25], further details will not be given here. Needless to say, new sequential processes based on SmE-promoted ketyl/olefin coupling reactions are still being developed (Eq. 75) [88]. 

Another class of chelation-controlled reactions involves Sml2, which has been used to mediate inter- and intramolecular ketone-olefin couplings [17], Matsuda and collaborators showed that coupling erpt/ira-) -hydroxyketone with acrylonitrile led exclusively to the anti diol under Sml2 reductive conditions [18]. Chelation control model J in Scheme 6 was proposed to account for the sense of diastereo-selectivity. In this model, chelation of the Smb to both the jff-hydroxy and the... 

The halogenated derivatives of six membered heterocycles, like their carbacyclic analogues, usually participate readily in coupling reactions that involve the incorporation of an olefin or carbon monoxide. The insertion of carbon monoxide commonly leads to the formation of either a carboxylic acid derivative or a ketone, depending on the nature of the other reactants present. Intermolecular and intramolecular variants of the insertion route are equally popular, and are frequently utilized in the functionalization of heterocycles or the formation of annelated ring systems. 

This C-H/olefin coupling can be extended to coupling with acetylenes [6], The reaction of aromatic ketones with internal acetylenes gives the ortho alkenylated product in high yield (Scheme 2), but reaction with terminal acetylenes does not afford the coupling product. With terminal acetylenes, dimerization of acetylenes occurs as a predominant reaction. 

In (C5Me5)Rh(C2H3SiMe3)2-catalyzed C-H/olefin coupling the effect of the coordination of the ketone carbonyl is different from that in the ruthenium-catalyzed reaction [10], In the rhodium-catalyzed reaction all C-H bonds on the aromatic ring are cleaved by the rhodium complex without coordination of the ketone carbonyl. Thus, C-H bond cleavage and addition of Rh-H to olefins proceed without coordination of the ketone carbonyl. After addition of the Rh-H species to the olefin, a coordinatively unsaturated Rh(aryl) (alkyl) species should be formed. Coordination of the ketone carbonyl group to the vacant site on the rhodium atom leads... 

Several related examples of transition metal-catalyzed addition of C-H bonds in ketones to olefins have been reported (Table 2) [11-14]. The alkylation of diterpenoid 6 with olefins giving 7 proceeds with the aid of Ru(H)2(CO)(PPh3)3 (A) or Ru(CO)2(PPh3)3 (B) as catalyst [11], Ruthenium complex C, Ru(H)2(H2)(CO) (PCy3)2, has catalytic activity in the reaction of benzophenone with ethylene at room temperature [12]. The alkylation of phenyl 3-pyridyl ketone 8 proceeds with A as catalyst [13], Alkylation occurs selectively at the pyridine ring. Application of this C-H/olefin coupling to polymer chemistry using ce,co-dienes such as 1,1,3,3-tetramethyl-l,3-divinyldisiloxane 11 has been reported [14]. 

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