Intramolecular Carbonyl Research Articles

Rhodium(II) catalyzed highly diastereoselective synthesis of conformationally restricted dispiro[1,3-dioxolane]bisoxindoles

Synthesis of conformationally restricted dispiro- and bis-dispiro-1,3-dioxolanes via three-component reaction of diazoamides, ketoamides/diketones, and aromatic/heteroaromatic aldehydes in the presence of rhodium(II) acetate dimer catalyst at room temperature involving carbonyl ylides is demonstrated with diastereoselectivity. Synthesis of macrocyclic dispiro-1,3-dioxolanes via intramolecular carbonyl ylide is also delineated in high yield. The conformationally restricted symmetrical as well as unsymmetrical dispiro-1,3-dioxolanes were obtained under mild conditions in a highly diastereo- and regioselective manner.

Synthesis of Multicyclic Heterocycles Initiated by C–H Bond Activation Along with “Rollover” Using a Rh(III) Catalyst

ABSTRACTVarious multicyclic heterocycles were synthesized via “rollover” as the key pathway using a Rh(III) catalyst with a catalytic amount of sodium pivalate or copper(II) acetate. 3‐Alkynyl‐2‐heteroarylpyridines were transformed into tri‐ or tetracyclic heterocycles containing two heteroatoms via an intramolecular alkyne insertion. 3‐Aryloyl‐2‐arylpyridines were derived into 4‐azafluoren‐9‐ols via the intramolecular carbonyl insertion.

Synthesis of conformationally restricted C2 symmetric macrodiolides via head to tail dimerization of carbonyl ylides

Tandem reaction of α-diazocarbonyl compounds in the presence of rhodium(II) acetate catalyst is described to furnish a range of conformationally restricted C2 symmetric macrodiolides via head to tail dimerization of intramolecular carbonyl ylides.

Stereocontrolled Synthesis of 1,3-Diols from Enones: Cooperative Lewis Base-Mediated Intramolecular Carbonyl Hydrosilylations

A streamlined synthesis of β-hydroxy ketone substrates has been developed to further investigate a recently discovered cooperative Lewis base-mediated intramolecular carbonyl hydrosilylation reaction. The synthesis features an enone β-borylation/oxidation sequence that has proven to be quite general and high-yielding. This has allowed for additional investigations into the diastereoselectivity of the hydrosilylation reaction through the preparation of important polyketide fragments.

ChemInform Abstract: An Efficient Synthesis of Pyrido‐Imidazodiazepinediones.

AbstractThe synthesis of optically pure heterocyclic scaffolds (V) (12 examples) is achieved through selective C‐acylation of the aminoimidazopyridine (I) with various amino acids and subsequent intramolecular carbonylation.

Successive C-C coupling of dienes to vicinally dioxygenated hydrocarbons: ruthenium catalyzed [4 + 2] cycloaddition across the diol, hydroxycarbonyl, or dione oxidation levels.

The ruthenium(0) catalyst generated from Ru3(CO)12 and tricyclohexylphosphine or BIPHEP promotes successive C-C coupling of dienes to vicinally dioxygenated hydrocarbons across the diol, hydroxyketone, and dione oxidation levels to form products of [4 + 2] cycloaddition. A mechanism involving diene-carbonyl oxidative coupling followed by intramolecular carbonyl addition from the resulting allylruthenium intermediate is postulated.

Toward the Total Synthesis of (±)-Andrastin C

An efficient approach to generate a fully functionalized cyclopenta[a]phenanthrene 34, the basic carbon framework of andrastin C (1c), is described. The present synthetic route features a stereoselective intramolecular Diels-Alder reaction of triene 12 and an intramolecular carbonyl ene reaction of 3-phenanthrenyl-2-(methoxymethoxy)propanal 31.

ChemInform Abstract: Intramolecular Carbonyl Nitroso Ene Reaction Catalyzed by Iron(III) Chloride/Hydrogen Peroxide as an Efficient Tool for Direct Allylic Amination.

AbstractTitle reaction is successfully applied to the oxidative ring closure of hydroxamic acids towards oxazolidinones, e.g. (II), (IV), (VI) and (X).

Synthesis of Fragrance Ingredients by Tandem Hydroformylation‐Cyclization of Limonene Catalyzed by Rhodium Complexes and Pyridinium p‐Toluenesulphonate

AbstractThe rhodium‐catalyzed hydroformylation of limonene (1) in the presence of PPh3 or P(O‐o‐tBuPh)3 as auxiliary ligands and pyridinium p‐toluenesulfonate, as an acid co‐catalyst, gave two diasteroisomers of 4,8‐dimethyl‐bicyclo[3.3.1]non‐7‐en‐2‐ol (3) in nearly quantitative yield. Limonene is a cheap natural product obtained commercially from citrus fruits, in particular, as a sub‐product of the orange juice industry; whereas alcohol 3 is an expensive perfume ingredient. Alcohol 3 is formed through the hydroformylation of 1 giving a corresponding aldehyde (2) followed by the intramolecular carbonyl ene reaction resulting in cyclization of the aldehyde. The cyclization step is highly stereoselective with only one diasteroisomer of 3 being formed from each of two diasteroisomers of 2. The use of the P(O‐o‐tBuPh)3 ligand not only remarkably accelerates the hydroformylation step compared to the system with PPh3, but also increases significantly the cyclization activity of the catalytic system.

Rhodium(II)-catalyzed intramolecular carbonyl ylide formation of α-diazo-β-ketoesters derived from N-phthaloyl-α-amino acids

Starting from L-alanine, L-phenylalanine, L-leucine, L-norleucine, or L-isoleucine, 2-diazo-3-oxo- 4-phthalimido-alkanoates 8 were prepared in three steps. Considerable racemization occurred at the stage of the 3-oxo-4-phthalimido-alkanoates 7. Dirhodium tetraacetate effectively catalyzed the intramolecular formation of carbonyl ylides 9, which in the absence of a trapping reagent underwent a (3+3) cycloaddition reaction to form the dimers 10. Carbonyl ylides 9 underwent (3+2) cycloaddition reactions with several electron-deficient alkenes and alkynes to give oxygen and nitrogen containing multicyclic systems 12-16. The keto group of the α-oxy-β-ketoester moiety of cycloadducts 2 and 12 is easily hydrated to give the gem-diol.

Intramolecular Carbonyl Nitroso Ene Reaction Catalyzed by Iron(III) Chloride/Hydrogen Peroxide as an Efficient Tool for Direct Allylic Amination

AbstractA mild, simple oxidation protocol employing iron(III) chloride as a catalyst and hydrogen peroxide as a stoichiometric oxidant was found to be compatible with an intramolecular carbonyl nitroso ene reaction and allowed us to efficiently convert hydroxamic acids into a diverse range of 1,2‐ and 1,3‐amino alcohol derivatives in a single operation.

Mn(III)-Mediated Formal [3+3]-Annulation of Vinyl Azides and Cyclopropanols: A Divergent Synthesis of Azaheterocycles

Mn(III)-mediated formal [3+3]-annulation has been developed using readily available vinyl azides and cyclopropanols with a wide range of substituents. Vinyl azides were successfully applied as a three-atom unit including one nitrogen to prepare pyridines and δ-lactams by the reactions with monocyclic cyclopropanols as well as to construct 2-azabicyclo[3.3.1] and 2-azabicyclo[4.3.1] frameworks with bicyclic cyclopropanols, bicyclo[3.1.0]hexan-1-ols, and bicyclo[4.1.0]heptan-1-ols. These reactions were initiated by a radical addition of β-carbonyl radicals, generated by the one-electron oxidation of cyclopropanols with Mn(III), to vinyl azides to give iminyl radicals, which cyclized with the intramolecular carbonyl groups. In addition, application of the present methodology to a synthesis of the quaternary indole alkaloid, melinonine-E, was accomplished.

Facile Synthesis of Dihydroquinoline‐Fused Canthines by Intramolecular Aza‐Diels–Alder Reaction

AbstractThe synthesis of dihydroquinoline‐fused canthines by intramolecular aza‐Diels–Alder reaction between N‐prenylated 1‐formyl‐9H‐β‐carbolines and substituted anilines in the presence of a Lewis acid, followed by oxidation, is described. Additionally, it has been found that the N‐protected aldehyde in the presence of a suitable catalyst [ZnBr2 or Yb(OTf)3] undergoes intramolecular carbonyl–ene reaction in a diastereoselective fashion to afford the syn or anti isomer of a new canthine derivative.

ChemInform Abstract: Remote Stereocontrol by Utilizing Intramolecular Carbonyl Reduction with Boranes.

ChemInform 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.

Enantioselective Cationic Polyene Cyclization vs Enantioselective Intramolecular Carbonyl−Ene Reaction

This paper describes highly efficient catalytic enantioselective cationic polyene cyclization and catalytic enantioselective intramolecular carbonyl-ene reaction in good to high yields with high enantioselectivities. The intimate relationship and mechanistic differences between the two enantioselective reactions were studied in detail. In addition, the cyclization products are versatile and useful building blocks for natural products and pharmaceuticals syntheses.

Intramolecular Carbonyl–Carbonyl Interaction as the Directing Motif of the Opposed Conformational Preferences Among [4 + 2] Cycloadducts of 3-Ethoxycarbonyl- and 3-Acetyl-Coumarins with 2,3-Dimethyl-1,3-Butadiene

In this work, the molecular structures of the Diels–Alder adducts: ethyl (6aR/S,10aR/S)-6a,7,10,10a-tetrahydro-8,9-dimethyl-6-oxodibenzo[b,d]pyran-6a-carboxylate C18H20O4 1 and (6aR/S,10aR/S)-6a-acetyl-6a,7,10,10a-tetrahydro-8,9-dimethyl-6-oxodibenzo[b,d]pyran C17H18O3 2; and the epoxide of this last (6aR/S,7aR/S,8aS/R,9aR/S)-6a-acetyl-6a,7,7a,8a,9,9a-hexahydro-7a,8a-dimethyl-6-oxo-6H-5,8-dioxacyclopropa[b]phenanthrene C17H18O4 3, are comparatively analyzed. Compound 1 is triclinic, space group P-1 with a = 7.7529(6) A, b = 9.8625(8) A, c = 11.3103(9) A, α = 109.387(9)°, β = 95.484(1)°, γ = 99.753(1)°, Z = 2. Compound 2 is monoclinic, space group Cc, a = 7.7285(7) A, b = 16.6813(15) A, c = 11.3213(10) A, β = 92.470(2)°, Z = 4. Compound 3 is monoclinic, space group P2 1 /c a = 11.2036(10), b = 15.8326(14), c = 8.3182(7), β = 90.600(2)°, Z = 4. The molecular structures of compounds 1–3 show conformational differences between lactone and 6a-acyl carbonyls. CO···CO dipolar interactions stabilize the less favoured syn conformation in 2–3, conclusions are supported on theoretical calculations. The molecular structure of compound 3 demonstrates that epoxidation of 2 leads to the stereo-selective addition of the oxygen atom. Conformation directed by carbonyl interactions] -->

Rhodium(I)‐Catalyzed Intramolecular Carbonylative [2+2+1] Cycloadditions and Cycloisomerizations of Bis(sulfonylallene)s

Novel [{RhCl(CO)dppp}(2)]-catalyzed intramolecular carbonylative [2+2+1] cycloadditions of bis(phenylsulfonylallene) derivatives under CO, leading to the facile formation of bis(phenylsulfonyl)bicyclo[n.3.0] frameworks (n=4-6), have been developed. The terminal double bonds of both allenyl moieties served exclusively as the two pi-components. In particular, this newly developed method was shown to be a powerful tool for the construction of bicyclo[6.3.0]undecadienones, which have hardly been prepared by the known Pauson-Khand (-type) reactions. The bicyclo[7.3.0]dodecadienone homologue (one extra carbon) could be formed in rather low yields. Alternatively, novel cycloisomerizations of bis(phenylsulfonylallene) derivatives with catalysis by the same Rh(I) complex under N(2) readily produced the 3,4-dimethylene-2,5-bis(phenylsulfonyl)cyclononene and the corresponding cyclooctene and cycloheptene frameworks.

Mn(III)-Mediated Reactions of Cyclopropanols with Vinyl Azides: Synthesis of Pyridine and 2-Azabicyclo[3.3.1]non-2-en-1-ol Derivatives

A Mn(III)-mediated divergent synthesis of substituted pyridines and 2-azabicyclo[3.3.1]non-2-en-1-ol derivatives was exploited using readily available vinyl azides and cyclopropanols with a wide range of substituents. In short, the reactions of vinyl azides with monocyclic cyclopropanol provided pyridines in the presence of Mn(acac)(3) (1.7 equiv), whereas those with bicyclic cyclopropanols led to the formation of 2-azabicyclo[3.3.1]non-2-en-1-ol derivatives using a catalytic amount of Mn(acac)(3). These reactions may be initiated by a radical addition of beta-keto radicals, generated by the one-electron oxidation of cyclopropanols, to vinyl azides to give iminyl radicals, which would cyclize with the intramolecular carbonyl groups. In addition, versatile transformations of 2-azabicyclo[3.3.1]non-2-en-1-ol to 2-azabicyclo[3.3.1]nonane or -non-2-nen frameworks were developed.

ChemInform Abstract: Sequence of Intramolecular Carbonylation and Asymmetric Hydrogenation Reactions: Highly Regio‐ and Enantioselective Synthesis of Medium Ring Tricyclic Lactams.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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.

Sequence of Intramolecular Carbonylation and Asymmetric Hydrogenation Reactions: Highly Regio- and Enantioselective Synthesis of Medium Ring Tricyclic Lactams

The intramolecular cyclocarbonylation reaction with palladium-complexed dendrimers on silica is a very effective method for the regioselective synthesis of methylene 8-, 9-, and 10-membered rings. The heterogeneous dendritic catalysts are easily recovered by simple filtration and reused for up to 10 cycles with only a slight loss of activity. Asymmetric hydrogenation of the resulting unsaturated heterocycles affords optically active tricyclic lactams in excellent yields and in high enantiomeric excess. This process can tolerate a wide array of functional groups, including halide, ether, nitrile, ketone, and ester. Moreover, the variation of heteroatom on the rings does not have any influence on the efficiency and enantioselectivity of the reaction.