Ketone-olefin coupling intramolecular

In 1986, Belotti, Pete and Portella reported that intramolecular ketone/olefin coupling could be achieved via photoinduced electron transfer (irradiation of an aliphatic ketone in HMPA)78. Several examples of this chemistry are highlighted below (Scheme 26). Intramolecular additions to C=C and allenes were also reported with yields in the range 70-80% however, additions to C=N were unsuccessful. 

Analogous intramolecular chelation-controlled ketone/olefin couplings with Sml2, in which Sm+3 was complexed in a cyclic manner to the ketyl anion and a /1-carbonyl of an ester or amide functionalilty, were reported as early as 1987 (Scheme 31)86. The cyclized samarium intermediate 49 could be further reacted with added electrophiles such... 

The intramolecular reductive ketone-olefin coupling was realized by Molan-der et al. by the combination SmI2/THF-f-BuOH [126]. For example, the spiro-... 

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... 

Intramolecular olefinic C-H/olefin coupling with the aid of Ru(CO)3(PPh3)2, which is also effective for the reaction of aromatic ketones with olefins, yields the carbocyclic compounds in excellent yield (Eq. 42) [67]. This type of cy-clization reaction can be extended to an asymmetric version when the [RhCl(coe)2]2/PPFOMe catalyst system is employed [68]. 

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. 

Dimerization of activated olefins or ketones as a means of ring closure was mentioned in Part I reports of more examples have been published.132 A special kind of coupling and ring closure occurs in the reduction of 6-phenyl-2,3-dihydrodiazepinium salt (76) in DMF to the diphenylpyrrolo-diazepine derivative (77). A plausible explanation of the formation of 77 involves dimerization of an initially formed radical, followed by intramolecular displacement of ethylenediamine.133-135... 

Molander et al. studied the intramolecular coupling of unactivated olefinic ketones by a reductive ketyl-olefin radical cyclization, mediated by Sml2 in the presence of HMPA [47] (Scheme 18). 

Studies by Molander et al. have demonstrated that samarium diiodide efficiently promotes the intramolecular coupling of ketones with distal epoxy olefins in the presence of HMPA, in good yields and often with high diastereoselec-tivity (Scheme 20). When tetramethylguanidine was used instead of HMPA, the desired carbocycle was obtained in good yield but the diastereoselectivity was diminished [55]. Evidence has been presented that suggests that the reaction proceeds via an initial radical cyclization route although reaction via an allyl samarium species cannot be ruled out. 

The bicyclic product is formed by coupling of the two radical sites, while the olefin results from a second intramolecular hydrogen abstraction. These reactions can be sensitized by aromatic ketones and quenched by typical triplet quenchers, and are therefore believed to proceed via triplet excited states. 

General Methods.—Among the methods now available for the direct synthesis of cyclopentanes via a [3 + 2] combination of carbon units, the iron carbonyl-promoted coupling between a,a -dibromo-ketones and olefins has always seemed especially attractive. This year sees the publication of a timely review by Noyori, the pioneer in this field, together with a report of the intramolecular version of the method [e.g. (43) -> (44) and (45) - (46)]. The palladium... 

The radicals R" generated by reduction of the halides RX (R = alkyl or aryl X = Cl, Br, I, etc.) by Sml2 (see Chap. 12.4.2) can be reduced (formation of RH by trapping an H atom from the solvent) or couple onto a carbonyl (aldehydes, ketones Barbier reaction), an olefin or an alkyne. For coupling reactions, the competitive reduction to RH indicated above must be avoided. The intramolecular coupling with formation of 5- or 6-atom rings, of synthetic interest, are promoted by the entropic factor. ... 

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