Intramolecular Insertion Reaction Research Articles

Asymmetric total synthesis of (+)-equilenin utilizing two types of cascade ring expansion reactions of small ring systems

Enantioselective synthesis of (+)-equilenin 1 utilizing two types of cascade ring expansion reactions of small ring systems is described. The first key step is an asymmetric epoxidation–ring expansion reaction of cyclopropylidene derivatives to afford chiral cyclobutanones. We found that both the fructose-derived chiral ketone and the chiral (salen)Mn(III) complex were effective catalysts for the asymmetric induction. The second key step is the palladium-promoted cascade ring expansion–intramolecular insertion reaction of the isopropenylcyclobutanol. Solvents were an important factor for the diastereoselective formation of hydrindanes. By utilizing these methodologies, the asymmetric total synthesis of (+)-equilenin 1 has been accomplished.

Carbene−Bridgehead Olefin−Carbene Rearrangement: Formation of the Tetracyclo[4.3.0.02,8.04,7]nonane Skeleton by Carbene CH Insertion1

The sequence of rearrangements of carbenes 6 has been studied. Precursors for 6 were 1-halo-3-(n-halomethyl)bicyclo[1.1.1]pentane derivatives 11, which were obtained by addition of polyhalomethanes to the central bond of [1.1.1]propellane derivative 13 via radical chain processes. Reaction of compounds 11 with MeLi or sodium bis(trimethylsilyl)amide generates carbenes 6, which are stabilized by a carbene (6)−bridgehead olefin−carbene (9) rearrangement, followed by an intramolecular CH insertion reaction of carbenes 9 to afford tetracyclononane derivatives 15 in good yields. The carbenes 6 show only slight preferences in the rearrangement to alkenes 7 and 8. Both could be trapped with α-methylstyrene as ene adducts 16 and 17. The strongly twisted bridgehead olefin 7 has only the option to rearrange to carbene 9, whereas 8 could give 9 or 10, but prefers to give 9, in accordance with results of DFT calculations. The tetracyclononanes 15c and 15d contain halide atoms in the 1,3-positions; on treatment with t...

Coupling of σ-acetylide ligands at Group 4 metallocene complexes to yield methylenecyclopropene-type frameworks

Treatment of a variety of bis(alkynyl)metallocenes Cp 2M(–CC–R) 2 (M=Ti, Zr, Hf; R=CH 3, n-C 3H 7, n-C 4H 10, cyclo-C 6H 11) with tris(pentafluorophenyl)borane yields the metallocene(μ-RC 4R)borate betaines 3. These seem to be in an endothermic equilibrium with their methylenecyclopropene derived isomers—by means of an intramolecular alkyne insertion reaction—which are very effectively trapped by the reaction with tert-butylisocyanide to yield the complexes 6 that exhibit a methylenecyclopropene derived σ-ligand framework. The zirconocene compounds 6a (R=CH 3), 6c (R= n-C 3H 7), 6d (R= n-C 4H 9), and 6e (R=cyclo-C 6H 11) were characterized by X-ray crystal structure analyses. The hydrolysis of 6a, 6c and 6d gave the respective metal free systems 7 that exhibit a pronounced cyclopropenylium–borate–betaine character.

Preparation of enantiomerically pure fructose-derived 1,3-oxazin-2-one by INIR methodology and its application as a chiral auxiliary in some model asymmetric reactions

A newly developed fructose-based homochiral 1,3-oxazin-2-one reagent prepared via a regioselective and stereoselective intramolecular nitrene insertion reaction (INIR) exerts smooth stereocontrol resulting in high levels of asymmetric induction and chemical yield in various synthetic transformations including aldol, Diels-Alder cycloaddition and α-bromination reactions.

Large Deuterium Isotope Effects for Intramolecular CH Insertion Reaction of 2-Alkylphenylnitrenes

Abstract The deuterium isotope effect for the intramolecular CH insertion reaction of the nitrene photolytically generated from 2-(2-phenylethyl)phenyl azide in cyclohexane is obtained as 14.7 ± 0.3 at 20 °C, which supports the hydrogen abstraction-recombination mechanism involving the triplet state nitrene. The temperature dependence of the isotope effect suggests the operation of the tunneling of the hydrogen atom in this process.

ChemInform Abstract: Anomalous Products from Intramolecular Insertion Reactions of Rhodium Carbenoids into the α‐C‐H Bonds of Ethers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Anomalous Products from Intramolecular Insertion Reactions of Rhodium Carbenoids into the α-C−H Bonds of Ethers

Anomalous Products from Intramolecular Insertion Reactions of Rhodium Carbenoids into the α-C−H Bonds of Ethers

Studies of the Reactions of 2-Substituted Dimethyl Benzoylphosphonates with Trimethyl Phosphite

Abstract Dimethyl benzoylphosphonates (1) react with trimethyl phosphite to give anionic intermediates (2) which decompose to give carbenes (3) and trimethyl phosphate [1]. When suitable ortho-substituents are present on the benzoylphosphonate, intramolecular carbene insertion reactions can occur to give cyclic systems. With alkyl substitutents, where the length of the chain provides a choice of cyclisation pathways, insertion into an appropriate C[sbnd]H bond to give a 5-membered ring has been found to be the preferred option. We have therefore been investigating the behaviour of systems, such as (4), where insertion into a C[sbnd]H bond to give a 5-membered ring is prevented.

Enantioselective Synthesis of a 1,2-Disubstituted Mitosene by a Copper-Catalyzed Intramolecular Carbon-Hydrogen Insertion Reaction of a Diazo Ester

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEnantioselective Synthesis of a 1,2-Disubstituted Mitosene by a Copper-Catalyzed Intramolecular Carbon-Hydrogen Insertion Reaction of a Diazo EsterHee-Jong Lim and Gary A. SulikowskiCite this: J. Org. Chem. 1995, 60, 8, 2326–2327Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://doi.org/10.1021/jo00113a008RIGHTS & PERMISSIONSArticle Views570Altmetric-Citations57LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (299 KB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

Highly regio- and stereo-specific preparation of a new carbohydrate-based 1,3-oxazin-2-one by the INIR method and its applications in some asymmetric transformations

Preliminary experiments show that a new gulonic acid-derived 1,3-oxazin-2-one, prepared by an intramolecular nitrene insertion reaction (INIR) method, serves to control both asymmetric aldol and Diels-Alder reactions with excellent stereo-selection.

Ligand Effects on the Chemoselectivity of Transition Metal Catalyzed Reactions of α‐Diazo Carbonyl Compounds

AbstractThe transition metal catalyzed reaction of α‐diazo carbonyl compounds has found numerous applications in organic synthesis, and its use in either heterocyclic or carbocyclic ring formation is well precedented. Early work in this area made use of insoluble copper catalysts. Although these catalysts are still employed today, their use has decreased significantly with the advent of homogeneous copper catalysts and catalysts based on other metals. The discovery that RhII carboxylates facilitate nitrogen loss from diazo compounds rekindled significant interest in the field of diazo/carbenoid chemistry. Since the realization that RhII carboxylates are superior catalysts for the generation of transient electrophilic metal carbenoids from α‐diazo carbonyl compounds, intramolecular carbenoid addition and insertion reactions have assumed strategic importance in CC bond‐forming reactions in organic synthesis. In contrast to other catalysts that are suitable for carbenoid reactions of diazo compounds, those constructed with the dirhodium(II) framework are most amenable to ligand modifications that, in turn, can influence reaction selectivity. This article will emphasize the chemical behavior of transition metal carbenoid complexes that are greatly affected by the nature of the ligand groups attached to the metal center. Much of the discussion will center on the ability of the dirhodium(II) ligands to determine reaction preference toward different functional groups on the same molecule.

A short synthesis of (±)-decarestrictine L

A stereoselective synthesis of (±)-decarestrictine L ( 1) from protected pentane-1,4-diol ( 2) is described. The key intermediate, tetrahydropyran-3-one 5a, was obtained by a tandem intramolecular carbenoid insertion and ylide rearrangement reaction.

Ligand Effects in the Rhodium(II)-Catalyzed Reactions of .alpha.-Diazoamides. Oxindole Formation is Promoted by the Use of Rhodium(II) Perfluorocarboxamide Catalysts

An improved procedure for the preparation of ethyl 2-diazomalonyl chloride was developed which involves the reaction of ethyl diazoacetate with triphosgene. Using this diazo acid chloride, it was possible to prepare a variety of diazoamides from substituted amines. The rhodium(II)-catalyzed decomposition of these diazoamides was studied in order to probe the chemoselectivity of the carbenoid intermediates in intramolecular insertion reactions. Rhodium(II) acetate decomposition of N-benzyl-2-diazo-N-phenylmalonamic acid ethyl ester resulted in intramolecular C-H insertion to give ethyl 1,4-diphenyl-2-oxoazetidine-3-carboxylate. By changing the catalyst ligand to trifluoroacetamide, β-lactam formation was completely suppressed in favor of the aromatic C-H insertion which produces an oxindole as the only detectable product. The competition between aliphatic and aromatic carbon-hydrogen insertion of 2-diazo-N-isobutyl-N-phenylmalonamic acid ethyl ester provides another example of ligand effectiveness in controlling chemoselectivity in dirhodium (II)-catalyzed metal carbene reactions. Thus, treatment of the N-isobutyldiazoanilide with rhodium(II) acetate results in exclusive aliphatic C-H insertion giving 4,4-dimethyl-2-oxo-1-phenylpyrrolidine-3-carboxylic acid ethyl ester, while the perfluorobutyramide ligand promotes oxindole formation by aromatic C-H insertion. Several other rhodium(II)-catalyzed reactions were studied and were studied and were found to be highly catalyst dependent, rhodium (II) perfluorocarboxamides promoting aromatic C-H insertion, and hence oxindole formation, over O-H insertion, cyclization onto adjacent triple bonds, or cyclization to generate 1,3-dipolar intermediates

A short new route to the pyrido[2,3,4-kl]acridine subunit common to pyridoacridine alkaloids of marine origin

A short new route to the pyrido[2,3,4-kl]acridine ring system has been developed from readily available quinoline precursors involving two key steps: (i) a palladium(0)-catalysed Suzuki cross-coupling reaction of 4-chloroquinolines with arylboronic acids, and (ii) an intramolecular nitrene insertion reaction of the nitrenes derived from 4-phenyl-5-azidoquinolines.

Successive formation of enaminoketene and arenetricarbonyl nitrogen ylid chromium complexes during intramolecular alkyne insertions into aminocarbene complexes

Upon heating, alkyne(aminocarbene) complexes [(CO)5CrC(NR1R2)(CH2)3CCPh] undergo an intramolecular insertion reaction to give, first, complexes containing enaminoketene coordinated to Cr(CO)3, and then arene tricarbonyl chromium nitrogen ylides, which finally lead to rearranged organic products. Both types of complex were fully characterized by X-ray analysis.

A carbenoid route to C(1)–C(11) bridged steroids

The exocyclic olefin 3 enters into stereoselective cyclopropanations with dihalocarbenes on the steroid β-face to afford the protected spiro[2.5]octane analogues 4 and 5. These intermediates are transformed into novel, highly strained steroid derivatives, like 9, by utilizing an intramolecular cyclopropylidene insertion reaction en route to pentacyclic, C(1)–C(11) ethano-bridged steroids 13–20.

Intramolecular hydrogen abstraction and insertion of singlet ethylnitrene

Two patterns of the 1,3-hydrogen migrations conceivable for singlet ethylnitrene, i.e. (a) the pure 1,3-hydrogen migration CH 3CH 2N→ C·H 2CH 2·N H and (b) the 1,3-hydrogen migration accompanying the ring closure CH 3CH 2N→CH 2CH 2NH, are compared theoretically. The minimum-energy paths for both intramolecular processes (a) and (b) are traced by the UHF and RHF SCF procedures, respectively, using the 4-31G basis set. Subsequent MRD-CI treatments show that the activation barrier heights are 115.5 and 21.8 kJ mol −1 for reactions (a) and (b), respectively. It is concluded that reaction (b), which can be regarded as an intramolecular insertion reaction, should be a well-defined low-barrier elementary process.

Cyclic Elimination and Intramolecular Insertion Reactions of Thermally-Generated Monomeric Metaphosphoric Esters (Metaphosphates)

Abstract 2-Aryl-1,3,2-dioxaphospholanes (aryloxyphosphites) decompose thermally in the gas phase with loss of ethylene to generate aryl metaphosphates which cyclise by intramolecular insertion (phosphonylation) or abstract a β-hydrogen to form a terminal alkene by loss of HPO3.

Carbene intermediates in the reaction of trialkyl phosphites with dialkyl aroylphosphonates: formation of novel quasiphosphonium ylides

Reaction of trialkyl phosphites with dialkyl aroylphosphonates leads to the formation of anionic intermediates which, in the absence of electrophiles, undergo cleavage at temperatures above about 80 °C to give carbene intermediates; these undergo intramolecular carbene insertion reactions or are trapped by trialkyl phosphites to give novel ylides.

An alternative synthesis of the 1-oxacephem skeleton

1-Oxacephem skeletons were constructed in a convergent manner starting from building blocks B and C , which were easily prepared from penicillin and diketene, respectively, followed by intramolecular carbene insertion reaction of the resulting intermediate A .