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This article discusses the development of a method for the intramolecular silylmethylation of aromatic C-H bonds using photoexcited palladium as a catalyst. The reaction allows for the introduction of a methyl or hydroxymethyl group onto complex molecules with associated biological activities. The authors optimized the reaction conditions and investigated the scope and limitations of the reaction, finding that a variety of benzylic alcohol derivatives could be efficiently converted into the corresponding siloxacycles. The authors also demonstrated that the carbon-silicon bond of the siloxacycle could be further modified through protodesilylation or oxidation. [Extracted from the article]

Author(s): Akira Sakakura [1]; Atsushi Ukai [1]; Kazuaki Ishihara (corresponding author) [1] Polycyclic bio-active natural products that contain halogen atoms have been isolated from a number of different marine organisms [...]

Ring-closing olefin metathesis is effective in the synthesis of highly strained ring systems. This strategy of direct cyclization of a strained inside-outside skeleton provides first synthetic access to optically active ingenol.

The synthesis of aplyronines A,B and C and their analogs is described. Aplyronine A is an antitumor substance isolated from Aplysia kurodai while aplyronines B and C are two natural congeners. The procedure involved an Evans aldol reaction and Sharpless epoxidation to build the C5-C11, C21-C27 and C28-C34 segments and the bridging of several segments to construct the C5-C20 and C21-C34. These were followed by a Julia olefinic reaction between the last two segments and a Yamaguchi lactonization to afford aplyronine A.

C 1-Symmetric chiral ammonium salt catalysts induced a kinetic resolution of racemic α-nitrolactones through an asymmetric ester–amide exchange reaction. The corresponding amides were obtained with high enantioselectivities and high S (= k fast / k slow) values. This reaction system is a useful approach for obtaining carbocyclic quaternary α-nitroamides as chiral building blocks. [ABSTRACT FROM AUTHOR]

An enantioselective Diels–Alder reaction of 3-nitrocoumarins has been developed. A tryptophan-derived C 1-symmetric organoammonium thiourea catalyst promoted the reaction of 3-nitrocoumarins with Danishefsky's diene to give the corresponding adducts with good enantioselectivity (up to 94% ee). One of the resulting adducts was converted into a chiral carbocyclic quaternary β-amino alcohol. [ABSTRACT FROM AUTHOR]

The enantioselective catalysis of 1,3-dipolar cycloaddition reaction of nitrones with propioloylpyrazole and acryloylpyrazole derivatives in presence of a chiral copper(II) complex of 3-(2-naphthyl)-L-alanine amide is described. The reaction is the first successful method for the catalytic enantioselective 1,3-dipolar cycloaddition of nitrones with acetylene derivatives.

Several studies are conducted to explain the rational design of the highly enantioselective asymmetric Diels-Alder catalysts that are shown to be bearing several 4,4'-sulfonamidomethyl groups. The secondary reactions taking place in the system are shown to be extremely useful for high catalytic activity and high level of induction of enantioselectivity.

The article discusses the commonly used DMAP (4-(N,N-dimethylamino)pyridine)-catalyzed esterification under different base- and solvent-free conditions.

The hydrophobic effect of diarylammonium sulfonates activated the esterification reaction, and steric hindrance suppressed the dehydrative elimination of secondary alcohols to produce alkenes. A direct catalytic ester condensation of carboxylic acids with an equimolar amount of primary alcohols without solvents at room temperature was obtained.