Cyclopropanes oxidative addition

Cyclopropane oxidative addition to low-valent transition metals has been intensively investigated in the decades since the first metallacyclobutane complex was prepared by this methodology <1996CHEC-II(lb)887>. Comprehensive reviews on this topic are available <1980CGR149, 1994CRV2241>. 

Following Bergman s initial report <1984JA7272, 1986JA7346>, cyclopropane C-H activation and subsequent isomerization of the intermediate tr-cyclopropylrhodium hydride 169 to the rhodacyclobutane complex 112 has been demonstrated for a tris(pyrazolyl)borate analogue (Scheme 39), confirming that net cyclopropane oxidative addition to rhodium follows a rather unexpected indirect mechanistic course <19980M4484>. 

Treatment of [Rh(CO)2Cl]2 with cyclopropanes 205) or cubanes 61) leads to an oxidative addition of the hydrocarbon to the Rh(I) species and is thought to involve CO insertion. 

Recently, Y. Yamamoto reported a palladium-catalyzed hydroalkoxylation of methylene cyclopropanes (Scheme 6-25) [105]. Curiously, the catalysis proceeds under very specific conditions, i.e. only a 1 2 mixture of [Pd(PPh3)4] and P(o-tolyl)3 leads to an active system. Other combinations using Pd(0 or II) precursors with P(o-tolyl)3 or l,3-bis(diphenylphosphino)propane, the use of [Pd(PPh3)4] without P(o-tolyl)3 or with other phosphine ligands were all inefficient for the hydroalkoxylation. The authors assumed a mechanism in which oxidative addition of the alcohol to a Pd(0) center yields a hydrido(alkoxo) complex which is subsequently involved in hydropal-ladation of methylenecyclopropane. 

Vaska s complex catalyzed the transformahon of aUenylcyclopropane into 2-alkenylidenecyclohex-3-enone under conditions of pressurized CO (Scheme 11.25) [38]. In this reaction, the jr-coordination to internal oleflnic moiety of the aUene brings the metal closer to the cyclopropane ring. Release of the cyclopropane ring strain then facilitates the oxidative addition of vinylcyclopropane moiety along with C-C bond cleavage, such that metallacyclohexene is obtained a subsequent carbonyl insertion and reductive elimination then provides the product Hence, the reaction can be recognized as a [5+1] cycloaddition of vinylcyclopropane and CO. 

It is assumed that the reaction proceeds by the oxidative addition of the carbon-carbon bond of the cyclopropane to cobalt species to form a metallacyclic intermediate. The regioselectivity of this reaction is controlled by the relative ease of insertion of the cobalt species into the C1-C2 and the C1-C3 bonds of the cyclopropane (Scheme 7). In the case of the reaction of the (1-R, 2k )-isomer trans-l5a, 5-methyl-3-phenyl-2-cyclopenten-1-one (17a) is produced via TS2 without any serious steric repulsion, while the 4-methyl isomer 16a must be pro-... 

Oxidative addition of the carbon-carbon bond of cyclopropanes to zero-valent cobalt species is not in general a facile process. It is assumed that in this reaction the alkynyl part of the molecule works as an anchor for the cobalt carbonyl, which enables an efficient insertion of the cobalt moiety into the proximal carbon-carbon bond of the cyclopropane to proceed. It therefore became a matter of interest to see whether direct connection of the alkynyl part with the cyclopropanol is essential or not for this type of reaction. 

Larsen, J., Rasmussen, B.S., Hazell, R.G. and Skrydstrup, T, (2004) Preparation of a novel diphosphine-palladium macrocyclic complex possessing a molecular recognition site. Oxidative addition studies. Chem, Commun., 202-203 Braunstein, P., Clerc, G. and Morise, X. (2003) Cyclopropanation and Diels-Alder reactions catalyzed by the first heterobimetallic complexes with bridging phosphinooxazoline ligands. New J. Chem., 27,68-72 Braunstein, P., Clerc, G., Morise, X., Welter, R. and Mantovani, G. (2003) Phosphinooxazolines as assembling ligands in heterometallic complexes. Dalton Trans., 1601-1605. 

Oxidative addition of RX to bis[dicarbonylrhodium(I)] porphyrins [317] (see Eq. 28) or monorhodium(I) porphyrins (Scheme 3, path m) also produces (T-bonded complexes. The organic substrates RX include aldehydes, anhydrides, aryl or acyl, arylcarbonyl, or ethoxycarbonylmethyl halides, cyclopropyl ketones [62] or highly strained cyclopropanes [318]. The fate of the second rhodium ion formulated as [Rh(CO)2]+ in Eq. (28) was not investigated. 

The palladium-catalysed intramolecular 3 + 2-cycloaddition of alk-5-enylidene-cyclopropanes produced a variety of bicyclo[3.3.0]octane systems with up to three stereocentres.62 The oxidative addition of cyclopropyl phenyl ketone to Ni(Pcy3) gave nickeladihydropyran, which is a key intermediate in the Ni(0)-catalysed homo-... 

Dimerization of ketone enolates. Frazier and Harlow1 have noted that ketone enolates (LDA or KH) couple to 1,4-diketones when oxidized by dry FeCl3 in DMF. Yields range from 25 to 70%. Paquette et al.2 have extended this reaction to intramolecular coupling of a bisenolate to a cyclopropane. Thus addition of a... 

However C—C addition may be preceded by C—H activation, as is seen with the oxidative addition of cyclopropanes or in cases where strained metallacycles may be formed 84... 

Most reactions of this type are considered to proceed by oxidative addition and cleavage of the C—C bond. For cyclopropane the reaction with [RhCl(CO)2]2 gives an isolable intermediate ... 

The S5mametry factors just described for the [2 - -2] cycloaddition process are general and apply equally to simple bond coordination and complete bond fusion (oxidative addition). The interacting bond can be either cyclopropane ring, for example, can assume a [2-1-2] interaction with a metal center to any point between the two extremes of simple coordination (7) and complete oxidative addition 8). In either situation, the symmetries of the bonding networks are... 

This review details the utility of copper compounds in a variety of organic transformations wherein their principal function is as a Lewis acid. Other important organic transformations such as conjugate additions, cyclopropanations, oxidations, and aziri-dinations are also mediated by copper species. Copper does not, however, function as a Lewis acid in these reactions but acts as a reagent and these reactions are not discussed here. The chemistry described in this review highlights the role of copper in facilitating synthetic transformations and the readers should consult the primary literature for experimental details. 

The oxidative addition of methylene- or allylidenecyclopropane to nickel(O) or palladium(O) can also lead to the formation of six-, seven-, and nine-membered metallacycles of nickeF " and palladium. Various substituted platinacyclobutanes (30) were obtained by oxidative addition of cyclopropanes to the complexes [CljPtLJj (Scheme... 

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