Application of Intramolecular Carbenoid Reactions in Organic Synthesis (original) (raw)
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Recent Advances on the Synthesis of Heterocycles from Diazo Compounds
Current Organic Chemistry, 2012
Carbenoids are transient species whose reactivity resembles that of free carbenes. They can be generated by several procedures, for instance, by the interaction of diazo compounds with transition metals, such as copper, ruthenium and rhodium complexes. They are able to react with various unreactive substrates, and their use has become very popular among synthetic organic chemists. The carbenoid transfer reactions are a powerful set of synthetic tools that have attracted attention due to their versatility in constructing several types of bonds and, thus, are used to create a complex skeleton framework. Several catalysts have been designed and employed to promote the decomposition of diazo compounds, making these reactions very useful in organic synthesis. This review intends to illustrate the research efforts that occurred in this field during the last four years, covering novel, biologically important compounds and methodologies involving carbenoid and non-carbenoid reactions from diazo compounds.
Tetrahedron Letters, 2004
A series of diazoketones tethered to tricarbonyliron coordinated dienes at the terminal position have been synthesized, and their decomposition reactions as carbene precursors studied. Intermolecular reactions with nucleophilic olefins were observed with Cu(acac) 2 as catalyst, the tricarbonyliron playing the role of an efficient protecting group of the diene fragment. With rhodium II acetate, intramolecular reactions predominate, with formation of five-membered rings, in the side chain, or less commonly, as a cyclopentenone joined side by side to a rearranged diene ligand. Unusually, due to cationic stabilization by the iron, six-membered rings in the side chain are also formed here. A still different reaction was observed during the thermal decomposition of a diazoketone tethered to a coordinated diene at position 2: the formation of a stable complex of a cyclohexa-2-4-dienone (iron assisted carbene reaction and multiple hydrogen migrations).
Metal salt catalyzed carbenoids—XV
Tetrahedron, 1976
Experimental and structural details are presented for the addition of bis-methoxycarbonyl carbene to a number of olelins employing homogeneous and heterogeneous catalyzed decompositions of dimethyl diazomalonate by copper and silver salts. The cyclopropanations are stereospecific and are accompanied by appreciable amounts of allylic C-H insertion products which could formally be derived from allylic radical or ionic intermediates. Cyclopropanation with cis 2-heptene proceeds 5.20 times as fast as with the trons isomer and cyclohexene reacts 4% times faster than l-methyl cyclohexene when the catalyst is iodo(trimethyl phosphite)copper(l). Metal salt catalyzed carbenoids-XV I2S9 Table I(a). Effect of catalyst upon yield in the reaction of dimethyl diazomalonate with cyclohexenes
Rhodium carbenoid mediated cyclizations of o-alkynyl-substituted .alpha.-diazoacetophenones
The Journal of Organic Chemistry, 1992
o-Akynyl-substituted a-diazoacetophenones undergo facile cyclization to indenone derivatives upon treatment with catalytic quantities of Rh(I1) carboxylates. A variety of structural influences were encountered by varying the nature of the substituent group attached to the alkyne carbon atom. The cyclization reaction involves addition of a rhodium stabilized carbenoid onto the acetylenic ?r-bond to generate a vinyl carbenoid. The vinyl carbenoid was found to undergo both CH and CC migration as well as 6-CH insertion into the alkyl backbone. Different catalysts were shown to result in significant variation in the product ratios for these reactions. Treatment of o-(b(ally1oxy)-1-pentyny1)-a-diazoacetophenone with rhodium(I1) mandelate afforded 2-(2-propen-l-y1)-2-(1oxo-vi-indenyl)-2,3,4,5-tetrahydrofuran in high yield. The formation of this compound involves initial formation of a vinyl carbenoid which reacts with the neighboring oxygen atom to give an oxonium ylide which subsequently undergoes a 2,3-sigmatropic rearrangement. When 2-ethynyl-a-diazoacetophenone is used, only produde derived from 6-endo closure are observed. Substituted 0-alkynyl a-diazoacetophenones give products derived from 5ezo cyclization. The mode of ring closure is controlled by both steric and electronic factors.
Resumen. Se describe la síntesis de la 2-diazo-1-[2-(2-tiofenilmetoxi)-fenil]-etanona (1) la cual involucra la reacción de sustitución nucleofílica aromática del (2-tiofenil) metóxido de sodio con 2-flurorobenzaldehído, la oxidación en condiciones suaves del grupo aldehído al ácido carboxílico y posteriormente la transformación a α-diazocetona a través de un anhídrido carbónico-carboxílico como intermediario de reacción. El tratamiento del compuesto 1 con cantidades catalíticas de acetato de rodio (II) da la tiofenilmetil benzofuranona 10 por medio de una transposición sigmatrópica [2,3] del iluro de oxonio 9 derivado del carbenoide de rodio que se postula como intermediario de reacción. Palabras clave: α-diazocetona, ciclización, carbenoide de rodio.