James W. Herndon

The chemistry of the carbon-transition metal double and triple bond: annual survey covering the year 2001

This is a review of papers published in the year 2001 that focus on the synthesis, reactivity, or properties of compounds containing a carbon-transition metal double or triple bond.

Reaction of alkynes with cyclopropylcarbene-chromium complexes : a versatile [4 + 2 + 1 - 2] cycloaddition reaction for the construction of cyclopentenones

The scope and limitations of the reaction between cyclopropylcarbene-chromium complexes and alkynes have been examined. A variety of cyclopropylcarbene complexes and alkynes have been employed in these studies. The reaction appears to be general for most simple alkynes, producing cyclopentenones. A mechanism has been proposed involving metallacyclobutene formation, electrocyclic ring opening, electrocyclic ring closure, CO insertion, alkene insertion, metallacyclopentene fragmentation, and cyclopentadienone reduction

Synthesis of Naphthalenes through Three-Component Coupling of Alkynes, Fischer Carbene Complexes, and Benzaldehyde Hydrazones via Isoindole Intermediates

The synthesis of naphthalene derivatives through three-component coupling of 2-alkynylbenzaldehyde hydrazones with carbene complexes and electron-deficient alkynes has been examined. The reaction involves formation of an isoindole derivative, followed by intramolecular Diels-Alder reaction, followed by nitrene extrusion. The reaction was highly regioselective using unsymmetrical alkynes.

Applications of carbene complexes toward organic synthesis

Abstract The article highlights advances in the discovery and development of reaction processes utilizing metal–carbene complexes which are useful in the field of synthetic organic chemistry. Emphasis is on reaction processes which result in the formation of carbon–carbon bonds in a reliable and efficient manner. Examples utilizing these reaction processes for the synthesis of biologically-important molecules has been noted wherever appropriate.

Synthesis of benzofurans through coupling of dienylacetylenes with carbene complexes: total synthesis of egonol

Abstract The reaction of various carbene complexes with dienylacetylenes has been examined. The reaction has been used as the cornerstone for the preparation of the nor-neolignan natural product egonol in five steps from readily available components. In most examples of the carbene–alkyne coupling, the reaction proceeds to form benzofuran derivatives. In the case of one highly functionalized terminal alkyne, a competing rearrangement/cyclization process occurs in preference to the carbene coupling process. The use of silylated alkynes subverts this process.

The chemistry of the carbon-transition metal double and triple bond: annual survey covering the year 1997☆

Abstract This survey is intended to be a comprehensive coverage of articles which report on the synthesis, reactivity, or properties of compounds which feature a multiple bond between carbon and a transition metal. Reactions which employ metal carbene complexes as transient intermediates generated through well-established routes are not covered unless there is some effort to characterize the carbene complex intermediate. Only compounds which feature a multiple bond between one carbon atom and one transition metal are discussed in this survey, thus bridging carbene and carbyne complexes are not covered unless there is a multiple bond to one transition metal. The complexes of stable carbenes with transition metals have not been included; since the π -donation component of these complexes is minimal, there is no formal carbon–metal multiple bond (J.C. Green, R.G.; Scurr, P.R. Arnold, F.G.N., Cloke, J. Chem. Soc. Chem. Commun. (1997) 1963; A.A. Danopoulos, D.M. Hankin, G. Wilkinson, S.M. Cafferkey, T.K.N. Sweet, M.B., Hursthouse, Polyhedron 16 (1997) 3879). This survey has been divided into two sections, metal carbene (or alkylidene) complexes and metal carbyne (or alkylidyne) complexes; the carbene complex section represents the vast majority of this article. The metal carbene section has been organized according to metal, starting from the left side of the Periodic Table. A special section focusing on alkene metathesis has been included prior to the discussion of carbene complexes of individual metals. The metal carbyne section has been organized according to reaction type.

Synthesis of benzofuran derivatives through the coupling of conjugated dienynes with Fischer carbene complexes

Abstract The reaction of Fischer carbene complexes with conjugated dienylacetylene derivatives followed by treatment with iodine leads to benzofuran derivatives in good-to-excellent yields. Equivalent products can be obtained from coupling of conjugated enediynes with Fischer carbene complexes in the presence of hydrogen atom donors.

Selective Remote Functionalization of Alkyl Side Chains in the Coupling of Fischer Carbene Complexes with Conjugated Enediynes

Abstract The reactions of various enediyne derivatives with Fischer carbene complexes has been examined. In most cases, benzofuran derivatives featuring a functionalized side chain were produced as a result of the coupling reaction. Reactions performed in chlorobenzene produced mostly this class of products. The major product was usually the alkene derivative, although in the presence of chlorine atom sources, chloride derivatives were also observed.

Effect of solvent polarity extremes on the coupling of cyclopropylcarbene-chromium complexes and alkynes: Synthesis of β-alkoxycyclopentadienones, 2-cyclopentene-1,3-diones, and cis 4,5-disubstituted cyclopentenones

Abstract The reaction between acetylenes and cyclopropylvarbene-chromium complexes in hexane affords exclusively cyclopentadienone derivatives in good yield, which are readily hydrolyzed to cyclopentenediones. The analogous reaction in 50:50 water dioxane affords cis disubstituted cyclopentenones.

Preparation of seven-membered rings by the reaction of cyclopropylcarbene-tungsten and molybdenum complexes with alkynes

Abstract The reaction between alkynes and cyclopropylcarbene-tungsten and molybdenum complexes has been examined. Depending upon the conditions of the reaction, either cycloheptadienones or furanones are obtained. The scope, limitation, and mechanistic rationale for observed selectivities are discussed.