Deprotection of a silyl group with mesoporous silica.

The triethylsilyl (TES) group of silyl ethers of several types is selectively and easily removed in the presence of a t-butyldimethylsilyl (TBDMS) group with a mesoporous silica MCM-41/MeOH heterogeneous system. Comparison of the efficiency was carried out among several solvents, and among such promoters as common zeolites and ion-exchange resins. Furthermore, FSM-16, another mesoporous silica, was examined for the possibility of recycling by re-calcination at 400 degrees C after the reaction.

Oxidative photo-decarboxylation in the presence of mesoporous silicas.

FSM-16, a mesoporous silica, was found to catalyze oxidative photo-decarboxylation of alpha-hydroxy carboxylic acid, phenyl acetic acid derivatives and N-acyl-protected alpha-amino acids to afford the corresponding carbonyl compounds. Furthermore, FSM-16 proved to be re-usable by re-calcination at 450 degrees C after the reaction.

Recyclable polymeric pi-acid catalyst effective on Mannich-type reaction in water.

Polymer-supported dicyanoketene acetal (poly-DCKA-1), synthesized by copolymerization of a DCKA bearing a 4-vinylbenzyl group with ethyleneglycol dimethacrylate, was found to be an excellent recyclable catalyst for the three-component Mannich-type reaction of aldehydes, aromatic amines, and TMS enolate of ethyl isobutyrate in water as the sole solvent.

[Development of polymer-supported pi-acid catalysts].

We reported that dicyanoketene acetals (DCKA), in which gem-dicyano groups of tetracyanoethylene (TCNE) are displaced with alkoxyl groups, function as pi-acid catalysts, and that a polymer (poly-DCKA-1) derived by copolymerization of a monomer, in which the alkoxyl group at the omega-position is modified with a styrene moiety, with ethyleneglycol dimethacrylate also shows high level of activities as a pi-acid. In this research, the effects of dicyanoketene ethylene acetal (DCKEA), polymers previously developed (poly-DCKA-1 and 2), new monomers, in which the alkoxyl group at the omega-position is modified with an ethereal moiety, and the corresponding polymers (poly-DCKA-3 and 4) were investigated on catalytic activities. Among the catalysts, the polymer (poly-DCKA-1) had the most efficient activity in monothioacetalization, cyanation, and Mukaiyama aldol reaction of acetals, two-component and three-component Mannich-type reaction, hydrolysis of acetals and silyl ethers, and two-component and three-component inverse electron demand Aza-Diels-Alder reaction. Remarkably, the polymer catalyst works more efficiently in water than in organic solvents and is recyclable.

Synthesis of (R)-(+)-tanikolide through stereospecific C-H insertion reaction of dichlorocarbene with optically active secondary alcohol derivatives.

Stereospecific alpha C-H insertion reaction of protected chiral 1,2-glycols, (S)-1,2-isopropylidenedioxytridecane (3) and ethyl (S)-4,5-isopropylidenedioxy-pentanoate (4), prepared from (R)-glyceraldehyde acetonide (2), with dichlorocarbene generated from CHCl(3)/50% NaOH/cetyltrimethylammonium chloride (as ptc.) took place with complete retention of configuration to provide (S)-4-dichloromethyl-2,2-dimethyl-4-undecyl-1,3-dioxolane (5) and ethyl (S)-3-(4-dichloromethyl-2,2-dimethyl-1,3-dioxolan-4-yl)-propanoate (8), respectively. The ester (8) was transformed to 5 by elongation of the side chain. The glycol derivative (5) was converted into O-TBDPS-protected (S)-2-hydroxymethyl-2-undecyloxirane (16). Reaction of 16 with a cuprate reagent containing homoallylic carbon chain followed by oxidative manipulation of the terminal olefin afforded (R)-(+)-tanikolide (1).

Synthesis of chiral sulfinyl-substituted 1-indolyl enones and asymmetric conjugate addition by an arylcopper reagent.

The asymmetric conjugate addition of arylcopper reagents to chiral 1-[2-(p-tolylsulfinyl)]indolyl and 1-[3-(p-tolylsulfinyl)]indolyl enones was examined. With the 2-sulfinyl-indolyl derivatives, the reaction of the arylcopper reagent gave high diastereoselectivities (81-88% de's) to afford the adducts in excellent yields, although the similar addition reaction of the 3-sulfinyl derivatives afforded poor diastereoselectivities.

Diastereoselective imino-aldol condensation of chiral 3-(p-Tolylsulfinyl)-2-furaldimine and ester enolates.

(Ss)-3-(p-Tolylsufinyl)-2-furaldimine was synthesized, and condensation of the chiral furaldimine with lithium ester enolates has been examined. The product distribution of the reaction is dependent upon reaction conditions and on the kind of the substituent placed on the esters. Disubstituted ester enolate resulted in the exclusive formation of (4R)-beta-lactam, while unsubstituted, tert-butyl ester enolate preferentially gave (3R)-beta-amino ester. With the monosubstituted ester enolates, the condensation afforded (4R)-beta-lactams and/or (3R)-beta-amino esters as major products. This method has been applied to an efficient route to chiral furyl beta-lactams.