Masatoshi Motoi

Isomerization of cyclic ethers having a carbonyl functional group: new entries into different heterocyclic compounds

Oxiranes (epoxides) and oxetanes having a carbonyl functional group are chemoselectively isomerized to different heterocyclic compounds via Lewis acid-promoted 1,6- and 1,7-intramolecular nucleophilic attacks of the carbonyl oxygen on the electron-deficient carbon neighboring the oxonium oxygen: for example, cyclic imides to bicyclic acetals, esters to bicyclic orthoesters, sec-amides to 4,5-dihydrooxazole or 5,6-dihydro-4H-1,3-oxazines, and tert-amides to bicyclic acetals or azetidines. The intramolecular attack of a 1,5-positioned carbonyl oxygen predominantly results in a propagating-end isomerization polymerization. On the other hand, cyclic ethers having a 1,8- or farther positioned carbonyl group undergo conventional ring-opening polymerization. A tetrahydrofuran (oxolane) ring does not open, even with a 1,6-positioned carbonyl group.

Asymmetric reduction of aromatic ketones with borane-amine complexes modified with optically pure 2,2′-dihydroxy-6,6′-dimethylbiphenyl

Highly enantioselective reduction of prochiral aromatic ketones was achieved with a chiral reagent (2) prepared from BH3·THF, optically pure 2,2′-dihydroxy-6,6′-dimethylbiphenyl (1), and an achiral amine.

Side Chain Liquid Crystalline Polyoxetanes with a Spacer-Separated Azobenzene Moiety. I. Preparation and Characterization.

Several oxetane derivatives carrying the azobenzene moiety at the C-3 position of the oxetane ring through the spacer arms of differing lengths were prepared by a substitution reaction of the corresponding bromide or p-toluenesulfonate residue of the oxetane with 4-hydroxyazobenzenes. The polymers of these oxetane derivatives were readily obtained by cationic ring-opening polymerization using the adequately increased amount of a THF· BF3 complex as an initiator at 20—30 °C. The liquid crystalline property of the polymers thus obtained were examined by differential scanning calorimetry and by optical polarized microscopy. From these measurements the influences of the p′-substituted azobenzene and of the spacer arm on the liquid crystalline property were found.

Chemoselective isomerization of amide-substituted oxetanes with Lewis acid to give oxazine derivatives or bicyclic amide acetals

The Lewis-acid catalyzed isomerization of secondary and tertiary amide-substituted oxetanes takes place chemoselectively, giving 5-hydroxymethyl-5,6-dihydro-4H-1,3-oxazines and reactive amide acetals consisting of a bicyclo[2.2.2]octane skeleton, respectively.

Substituent Effect on the Cationic Monomer-Isomerization Polymerization of (Cyclic Imide)-Substituted Oxetanes with Two Different Ring-Opening Routes

This study reports the effect of substituent on the cationic monomer-isomerization ring-opening polymerization of 3-(R 1 -methyl)-substituted 3-R 2 -oxetanes (1), in which R 1 is phthalimide, maleimide, succinimide, or glutarimide and R 2 is ethyl, benzyl, phenyl, or isopropyl. The acid-catalyzed polymerization of 1 gave polyacetal (3) or polyether (4), together with an isomeric bicyclic acetal (2). The isomerization of 1 to 2 took place prior to polymerization. Subsequently the polymerization of 2 occured by either single or double ring opening depending on temperature. The polymerization mechanism is discussed in detail based on the coordination of 1 to Lewis acid and the substituent effect on the polymerization manner. In the double ring-opening polymerization of 2 at 130°c, a carbon-carbon double bond of the lactam ring was indispensable for stabilizing the carboxonium-propagating end. Therefore, 2 carrying a saturated lactam ring did not polymerize in such a manner. Phenyl-substitued oxetane phthalimide was unique in undergoing an unusual cyclodimerization at 130°C, primarily because of the high susceptibility of the neophyl-type carbon skeleton to a cation transfer. On the other hand, most 2 brought about the single ring-opening polymerization below room temperature, regardless of the lactam substituent and the R 2 group. This polymerization was an equilibrium polymerization through a bicyclic oxonium-propragating end, and the thermodynamic parameters of polymerization were determined. Thus, 3 was transformed into 4 in one pot, by a combination of the depolymerization of 3 and the repolymerization of 2 above the ceiling temperature. From the structure analysis of 2 it was inferred that the single ring-opening polymerizability arises from dipole-dipole repulsion between the parallel standing lone pairs of two acetalic oxygen atoms in a nearly symmetric bicycle. There fore, 2 having a somewhat twisted bicyle showed no single ring-opening polymerizability.

Unusual cyclodimerization of small cyclic ethers via neighboring carbonyl-group participation and cation transfer

Oxetanes having both a carbonyl functional group and a phenyl group at the 3-position bring about unusual cyclodimerization under the influence of trifluoromethanesulfonic acid, to give a cis/trans-isomer mixture of substituted 1,3-dioxanes via neighboring carbonyl-group participation, cation transfer including phenonium rearrangement, and cyclodimerization. Oxiranes having a carbonyl functional group also undergo a similar cyclodimerization to form a 1,3-dioxolane ring. No phenyl substituent is required in the cases of the oxiranes, because the cation transfer process involves a 1,2-hydride shift alone. These five- and six-membered cyclic acetals are quite different from ring-expanded cyclic ether dimers expected simply from the back-biting reaction known in the cationic ring-opening polymerization of oxiranes and oxetanes.

Preparation and diazo-coupling reaction of the pendant spacer-separated aniline residue based on a polyoxetane network

Abstract Polyoxetane networks anchoring the pendant spacer-separated aniline residue were prepared in good yield by a BF 3 -initiated ring-opening polymerization of the corresponding succinyl-protected oxetane monomer with a bisoxetane, as a crosslinking agent, followed by alkaline hydrolysis of the crosslinked product. Diazo-coupling reactions of the pendant aniline residue were examined with phenol and resorcinol, and the formation of desired polymers was confirmed by comparing the structures between the polymer products and the authentic polymers by IR and 1 H-NMR spectroscopy.

Chiral discrimination towards racemic alcohols through Host/Guest clathrate inclusion with axially chiral 1,1′-binaphthyl-2,2′-dicarboxylic acid

Axially chiral 1,1′-binaphthyl-2,2′-dicarboxylic acid (1) was successfully utilised as a new type of chiral host molecule soluble in aqueous alkaline solution; 1-phenylalkan-1-ols were optically resolved by means of chiral host/guest clathrate inclusion giving optical purities ranging from 18 to 90% enantiomeric excess (e.e.), depending on the alkyl group.

Asymmetrie selection polymerization of (RS)-α-methylbenzyl methacrylate with axially chiral catalysts prepared from grignard reagents and biphenyl derivates

SummaryAsymmetric selection (stereoelection) polymerization of racemic α-methylbenzyl methacrylate (MBMA) was investigated by using axially dissymmetric catalysts in toluene. The catalysts of binary system, which were prepared in situ from optically pure 2,2′-diamino-6,6′-dimethylbiphenyl (1) or its N-methylated derivatives and Grignard reagents (RMgX). The selection depended upon not only the kinds of the amines and RMgX but also the molar ratios. Among the catalysts examined, cyclohexylmagnesium bromide (cHexMgBr) — (R)-1 [1.5/1.0 molar ratio] system gave the best selection and it polymerized (S)-monomer preferentially over (R)-antipode.

Preparation of Polyoxetane-Crosslinked Polystyrenes Useful as Polymeric Supports with Pendant Functional Groups.

側鎖スペーサー末端にイミドやエステル基をもち, ポリエーテルで架橋したポリスチレン樹脂が, スチレンモノマーとビスオキセタンのカチオン共重合で容易に調製できる. 樹脂側鎖末端基はアルカリ加水分解条件で有用官能基へさらに変換する. 同じ側鎖構造をもつスチレンとオキセタンのコポリマーおよび両ホモポリマーのブレンド物についての示差走査熱量分析および偏光顕微鏡観察結果は, 両モノマーの共重合性を強く示唆した.