Rhodium-Catalyzed Cycloisomerization Research Articles

Insights into the mechanism and selectivity of the Rh(i)-catalyzed cycloisomerization reaction of benzylallene-alkynes involving C–H bond activation

The detailed reaction mechanisms of rhodium-catalyzed cycloisomerization of benzylallene-terminal alkynes involving Csp2−H bond activation on the benzyl phenyl ring have been investigated with the aid of density functional theory calculations.

Rhodium-Catalyzed Dehydrogenative Cycloisomerization of Dienylcyclopropane to Highly Substituted Toluene.

A rhodium-catalyzed dehydrogenative cycloisomerization of dienylcyclopropane compounds is reported, which provides a straightforward approach to a variety of highly substituted toluene derivatives in 67-85% yields. The dienylcyclopropane-imides are produced by a single-step formal three-component olefination procedure. Preliminary mechanistic studies indicated that an electron-withdrawing group as R plays a critical role in completing this transformation.

Highly Diastereoselective Hydrosilane-Assisted Rhodium-Catalyzed Spiro-Type Cycloisomerization of Succinimide and Pyrazolone-Based Functional 1,6-Dienes.

Organosilicon compounds are important reagents and synthetic intermediates that play a key role in the construction of new materials and complex products. Here we show a highly diastereoselective rhodium-catalyzed cycloisomerization of 1,6-dienes, in which the use of (EtO)3 SiH accelerates the intramolecular cyclization reaction to afford a novel spiro-fused succinimide and pyrazolone derivatives in moderate to excellent yields as a single diastereoisomer. The proposed mechanism involves an active Rh-H species from the hydrosilane that is the H-donor in this spiro-type cycloisomerization reaction.

Substituent-dependent generation of tricyclic frameworks by the rhodium-catalyzed cycloisomerization of homopropargyl allene-alkynes: a theoretical study.

Polycyclic compounds having biological activities can be modified by employing different substituents. Substituent-dependent generation of tricyclic frameworks by the rhodium-catalyzed cycloisomerization of homopropargyl allene-alkynes was investigated by using density functional theory calculations. A mechanistic study revealed that all the three reactions, A (Z = Me, X = tBu), B (Z = Me, X = Me), and C (Z = H, X = Me), underwent initial oxidative cyclization, from which the divergent cycloisomerization was triggered when different substituents were employed. It was found from our calculations that reactions A and B underwent alkyne insertion into the Rh-C(sp2) bond and resulted in a key metal carbenoid intermediate. From the metal carbenoid species, reaction A bearing a more hindered tert-butyl group prefers 1,2-hydrogen migration to produce a 6/5/4 tricyclic product, while reaction B bearing a less hindered methyl group prefers 1,2-carbon migration leading to ring expansion and producing a 6/5/5 tricyclic product. The origins of the distinct selectivity were disclosed, which are beneficial for the development of novel related reactions. For reaction C (Z=H, Z=H or Z=H, Z=Me), the β-hydrogen elimination was found to be favored over the alkyne insertion into the Rh-C(sp2) bond and thus the monocyclic product is delivered. The E/Z effects involved in the above two cases were also discussed.

Rhodium-catalyzed cycloisomerization of ester-tethered 1,6-diynes with cyclopropanol moiety leading to tetralone/exocyclic diene hybrid molecules.

The rhodium-catalyzed cycloisomerization of ester-tethered 1,6-diynes bearing a cyclopropanol moiety produced tetralone/exocyclic diene hybrid molecules with thermodynamically unfavorable alkene geometry. The results of control experiments and density functional theory calculations suggest that the ester tether plays an important role in the efficiency of E/Z isomerization processes.

Sequentially rhodium-catalyzed enantioselective cycloisomerization–hydrogenation syntheses of alkylidene butyrolactone β-hydroxyethanes and alkylidene tetrahydrofuran β-aminoethanes

The enantioselective Rh-catalyzed Alder-ene cycloisomerization of ester- and ether-tethered alkyne allyl alcohols is an excellent entry to subsequent Rh-catalyzed one-pot hydrogenations in the sense of sequentially Rh-catalyzed processes to chiral alkylidene butyrolactone β-hydroxyethanes and alkylidene tetrahydrofuran β-aminoethanes, respectively, with excellent levels of enantioselectivity.

Reaction Discovery Using Neopentylene-Tethered Coupling Partners: Cycloisomerization/Oxidation of Electron-Deficient Dienynes.

A rhodium-catalyzed cycloisomerization and oxidation of tethered dienynes for the synthesis of indanes is described. An auxiliary fragmentation/olefination method (also described herein) provides novel access to tethered alkyne-dienoate substrates. The reported method circumvents current limitations in and expands the scope of inverse-demand Diels-Alder-type cycloadditions. Traditional discovery substrates involving malonate-, ether-, and sulfonamide-based tethers are problematic in the current methodology, underscoring the unique virtue of neopentylene-tethered substrates for reaction discovery.

Ken Tanaka

Ken Tanaka

ChemInform Abstract: Rhodium‐Catalyzed Cycloisomerization of 2‐Alkynyl‐N′‐arylidenebenzohydrazides Through exo‐Carboamination.

The rhodium-catalyzed cycloisomerization reaction of 2-alkynyl-N′-arylidenebenzohydrazides is reported. The reaction provides 4-alkenylphthalazin-1(2 H)-ones through an intramolecular exo-carboamination.

Rhodium-Catalyzed Asymmetric Cycloisomerization of (E)-1,6-Enynes

Rhodium-Catalyzed Asymmetric Cycloisomerization of (E)-1,6-Enynes

Rhodium-Catalyzed Enantioselective Cycloisomerization to Cyclohexenes

Rhodium-Catalyzed Enantioselective Cycloisomerization to Cyclohexenes

Rhodium-Catalyzed Asymmetric Cycloisomerization of 1,6-Enynes

Rhodium-Catalyzed Asymmetric Cycloisomerization of 1,6-Enynes

Total Synthesis of Acetylaranotin via Rhodium-Catalyzed Cycloisomerization

Key words azomethine ylides - 1,3-dipolar cycloaddition - rhodium-catalyzed cycloisomerization - dihydrooxepines - epidithiodiketopiperazines

Chiral Tridentate Ligand for Rhodium-Catalyzed Cycloisomerization

Chiral Tridentate Ligand for Rhodium-Catalyzed Cycloisomerization

Interception of a Rautenstrauch Intermediate by Alkynes for [5+2] Cycloaddition: Rhodium‐Catalyzed Cycloisomerization of 3‐Acyloxy‐4‐ene‐1,9‐diynes to Bicyclo[5.3.0]decatrienes

Interception of a Rautenstrauch Intermediate by Alkynes for [5+2] Cycloaddition: Rhodium‐Catalyzed Cycloisomerization of 3‐Acyloxy‐4‐ene‐1,9‐diynes to Bicyclo[5.3.0]decatrienes

Rhodium-Catalyzed Asymmetric Cycloisomerization of 1,6-Enynes

1,6-Enynes can be converted into bicyclo[4.1.0]heptene derivatives via 6-endo-dig cycloisomerization catalyzed by π-acidic metals. Despite the high synthetic utility of this transformation, there have been only few asymmetric variants reported so far. In this paper the authors describe a rhodium-catalyzed cycloisomerization of oxygen- and nitrogen-bridged 1,6-enynes proceeding with high yields (71-94%) and enantio­selectivities (68-99% ee). Substituted tetrafluoro­benzobarrelene (TFB, 1) was found to be the optimum ligand showing high catalytic activity presumably due to its high π-accepting ability. It can be expected that the unique catalyst design will be suitable for other applications of transition-metal catalysis.

Rhodium-catalyzed synthesis of γ-butyrolactams and pyrrolidines via cycloisomerization of N-tethered 1,6-enynes

A rhodium-catalyzed cycloisomerization reaction of N-tethered 1,6-enynes with an intramolecular halogen shift has been developed, providing a useful process for the synthesis of stereo defined γ-butyrolactam and pyrrolidine derivatives in good to excellent yields. Effects of both electronic feature and steric structure of the substrates on the outcome of the reaction were investigated.

Rhodium-Catalyzed Asymmetric Enyne Cycloisomerization

Rhodium-Catalyzed Asymmetric Enyne Cycloisomerization

Rhodium-Catalyzed Cycloisomerization of 1,6-Enynes

Rhodium-Catalyzed Cycloisomerization of 1,6-Enynes

Rhodium‐Catalyzed Cycloisomerization: Formation of Indoles, Benzofurans, and Enol Lactones

Internal affairs: Indoles, benzofurans, and enol lactones are formed chemoselectively from the rhodium-catalyzed cycloisomerization reaction of easily prepared alkynyl aniline substrates (see scheme, cod=cycloocta-1,5-diene, DMF=N,N-dimethylformamide). The reaction may proceed by nucleophilic capture of a vinylidene intermediate. Indoles are formed under mild conditions using low catalyst loadings.