Lewis Acid-Catalyzed Conjugate Addition−Cyclization Reactions of Ethenetricarboxylates with Substituted Propargyl Alcohols: Stereoselectivity in the Efficient One-Pot Synthesis of Methylenetetrahydrofurans

Oxygen-containing heterocyclic systems are important structures in organic chemistry because of their presence in many biologically active compounds. In this work, a Lewis acid-catalyzed cyclization of ethenetricarboxylate derivatives 1 with substituted propargyl alcohols to give methylenetetrahydrofurans was investigated. Reaction of 1 and gamma-silicon-substituted propargyl alcohols 4 with ZnBr2 at 80-110 degrees C led to (Z)-silicon-substituted products stereoselectively. Reaction of 1 and gamma-ester-substituted propargyl alcohol 7 in the presence of various Lewis acids gave ester-substituted methylenetetrahydrofurans stereoselectively. Interesting Lewis acid dependency on stereoselectivity for the reaction of 7 was found. Reaction of alpha-substituted propargyl alcohols also gave cyclized products.

Design and Synthesis of Novel C2-Symmetric Chiral Piperazines and an Application to Asymmetric Acylation of σ-Symmetric 1,2-Diols

[Structure: see text] A novel alicyclic chiral C2-symmetric piperazine, (S,S)-7, is designed and synthesized from L-proline. Benzoylation of a series of cyclic and acyclic meso-1,2-diols with a catalytic amount of (S,S)-7 and CuCl2 provided optically active monobenzoates with high enantioselectivity.

Zinc- and Indium-Promoted Conjugate Addition−Cyclization Reactions of Ethenetricarboxylates with Propargylamines and Alcohol: Novel Methylenepyrrolidine and Methylenetetrahydrofuran Syntheses

A new zinc- and indium-promoted conjugate addition-cyclization reaction to afford nitrogen- and oxygen-containing five-membered heterocycles has been developed. Reaction of ethenetricarboxylates with propargylamines (1 equiv) in the presence of ZnBr2 or InBr3 afforded methylenepyrrolidines in high yields. The stoichiometric use of ZnBr2 or InBr3 at room temperature and the catalytic use of InBr3-Et3N at 80 degrees C were effective. Reaction of ethenetricarboxylates with propargyl alcohol in the presence of ZnBr2 or InBr3 afforded methylenetetrahydrofurans.

Asymmetric [2+2] photocycloaddition of cycloalkenone–cyclodextrin complexes to ethylene

The enantioselective [2+2] photocycloaddition of cycloalkenone-cyclodextrin complexes to ethylene was examined. Photoreaction of alpha-, beta-, and gamma-cyclodextrin complexes of various cyclohexenonecarboxylates and cyclopentenonecarboxylates in the presence of ethylene in the solid state or in aqueous suspension gave corresponding photocycloadducts with chiral induction.

Facile Preparation of a New BINAP-Based Building Block, 5,5‘-DiiodoBINAP, and Its Synthetic Application

[reaction: see text] Bis(pyridine)iodonium tetrafluoroborate was successfully used for regioselective iodination of BINAP dioxide to give 5,5'-diiodoBINAP dioxide in an excellent yield of 92%, with no observed formation of 4,4'-diiodoBINAP dioxide. A Sonogashira cross-coupling reaction with 5,5'-diiodoBINAP dioxide gave the desired bis(trimethylsilylethynyl) product in 86% yield. The resulting 5,5'-disubstituted BINAP dioxides were reduced to the corresponding phosphines, which were used as chiral ligands for rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to 2-cyclohexenone to give 3-phenylcyclohexanone in excellent yield with high enantioselectivity.

Evolution of carbonylation catalysis: no need for carbon monoxide

Progress in organometallic catalysis began with the discovery of the Roelen reaction (hydroformylation with carbon monoxide and hydrogen) in 1938 and the Reppe reaction (hydrocarboxylation with carbon monoxide and water) in 1939. Since then, carbonylation chemistry by using carbon monoxide has occupied a central position in organometallic chemistry, as it relates to organic synthesis. There is, however, the problem of using gaseous carbon monoxide (a toxic greenhouse gas) in this chemistry. Recently, some strategies that address this issue have appeared. This minireview describes carbonylation reactions that can be conducted without the direct use of carbon monoxide. These carbonylation reactions provide reliable and accessible tools for synthetic organic chemists.

An Alternate Route for the Synthesis of Hybrid Mesoporous Organosilica with Crystal-Like Pore Walls from Allylorganosilane Precursors

The bridged allylorganosilanes 1,4-bis(diallylethoxysilyl)benzene and 1,4-bis(triallylsilyl)benzene are presented as new precursors for the surfactant-assisted synthesis of ordered mesoporous organosilica with pore walls having crystal-like molecular-scale periodicity. This approach provides a new route to the formation of periodic mesostructures with crystal-like pore walls. The synthesis method presented is applicable to the preparation of mesoporous organosilica with bulky organic groups, the precursors of which are typically impossible to obtain in high purity.

Rh(i)-catalyzed CO gas-free cyclohydrocarbonylation of alkynes with formaldehyde to α,β-butenolides

The rhodium(I)-catalyzed reaction of alkynes with formaldehyde proceeds via the double incorporation of a carbonyl moiety from formaldehyde, resulting in a CO gas-free cyclohydrocarbonylation leading to alpha,beta-butenolides.

Novel Enhancement of Diastereoselectivity of [2 + 2] Photocycloaddition of Chiral Cyclohexenones to Ethylene by Adding Naphthalenes

The additive effect on the diastereoselective [2 + 2] photocycloaddition of chiral cyclohexenones 1 to ethylene is examined. A novel and fairly efficient method of increasing the diastereoselectivity in the reaction of 1a was elucidated. The de value increased from 56% to 83% by the addition of 1-phenylnaphthalene. The major product 2a was isolated by the recrystallization of the diastereomeric mixture (major/minor = 11/1), of which X-ray analysis confirmed the absolute configuration of the bicyclic system of 2a. Hydrolysis for removing the chiral auxiliary and subsequent esterification afforded the optically pure bicyclo[4.2.0]octanone derivative 5. From the fluorescence spectral analyses and other experimental results, the additive effect is attributed to the complex formation of chiral cyclohexenone 1a and added naphthalenes.

Mechanism for degradation of poly(sodium acrylate) by bacterial consortium no. L7-98

Poly(sodium acrylate) (PSA) can be degraded by consortia of several bacterial species. We investigated the degradation mechanism for PSA (average molecular weight, 2100) by consortium no. L7-98. PSA was used as the sole carbon source in a mineral salt medium. After cultivation, the PSA had a range of molecular weights, including low-molecular-weight compounds, which were purified by gel-permeation and reversed-phase column chromatography. One purified compound, B1, with the molecular weight of 200, had a carbonyl group next to the terminus, according to 1H and 13C nuclear magnetic resonance spectrometry and X-ray analysis of the crystal structure. Two categories of metabolites of PSA were detected in the culture by electrospray ionization mass spectrometry. Results of high-resolution mass spectrometry (HR-MS) suggested that one kind of compounds had a carbonyl group and that the other kind of compounds had an aldehyde group and a double bond. Compounds having the molecular weights of 200 and 272 were rapidly produced from an acrylic acid oligomer with the molecular weight of 258 by resting cells of the consortium. HR-MS showed that a methylene group at the terminal unit was oxidized to a carbonyl group and that the compound with the molecular weight of 200 was compound B1. From these results, we propose that the degradation pathway of PSA involves (i) oxidation of a methylene group to a carbonyl group next to the terminus, (ii) decarboxylation to form an aldehyde group and dehydrogenation to form a double bond between the terminal unit and the next unit, and (iii) oxidation of the aldehyde group to a carboxyl group followed by elimination of an acetic acid.