Triphenylvinylphosphonium salts were prepared by the reaction of triphenylphosphine with epoxide and acid, followed by the addition of acetyl chloride in one pot operation. These salts were also synthesized by the reaction of 2-hydroxyalkyltriphenylphosphonium salts with acetyl chloride or oxalyl chloride. Other synthetic methods of these salts were also described. Optically active 3-hydroxyalkyl triphenyl phosphonium salts were synthesized by the reaction of phospho-rus ylides with epoxides. The reaction of these salts with 2 eq of BuLi gave the corresponding γ-oxidephosphonium ylides, which further reacted with aldehydes to give the corresponding E-rich homoallylic alcohols. 2, 2, 2-Tripheny1-1, 2λ⁵-oxaphospholanes were easily prepared by the reaction of 3-hydroxylalkylphosphonium salts with sodium hydride. The reaction with aldehydes afforded Z-rich homoallylic alcohols almost quantitatively. Thus, high selectivity for Z- or E-homoallylic alcohols was available depending on the particular circumstances. The syntheses of optically active methylenecyclopropylacetic acid and recifeiolide were succeeded by this method.

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Aromatic secondary amides such as benzanilide (1) exist in trans-amide form both in the crystal and in solution, whereas N-methylbenzanilide (2) exists in cis form in the crystal, and predominantly in cis form in various solutions. Similar cis conformational preferences were observed in the aromatic N, N'-dimethylated urea (4) and guanidine (7), in which two aromatic rings are located face-to-face. The cis conformations of N-methylated amides, ureas and guanidines could be utilized to construct interesting aromatic architecture. First, N, N', N″-trimethyl-N, N', N″-triphenyl-1, 3, 5-benzenetricarboxamide (12) and a cyclic triamide 14 have crystal structures in which three N-phenyl groups exist with the same orientation (syn conformation). Second, several aromatic amides which have no fixed asymmetric center afforded chiral crystals by simple recrystallization. In the case of 1, 2-bis (N-benzoyl-N-methylamino) benzene (18), two enantiomeric crystals could be distinguished morphologically or on the basis of symmetrical CD spectra in KBr, and by ¹H-NMR in the presence of chiral 1, 1'-bi-2-naphthol. Third, aromatic multi-layered structures could be constructed by using N, N'-dimethylated urea or guanidino bonds. These unique layered structures could be applied to obtain aromatic molecules with potent DNA-binding ability.

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Almost perfect enantio-differentiating hydrogenation was achieved by heterogeneous catalyst. Tartaric acid-NaBr modified supersonicated Raney nickel (TA-NaBr-MRNiU) showed 98.6% of e.d.a. in the hydrogenation of methyl 3-cyclopropyl-3-oxopropanoate. Three emprical modeles; “catalyst region model”, “reaction process model”, and “stereochemical model”, proposed for the explanation of the functions of MNi enable us to design the present reaction system. The development of the models and their contribution for the improvement of the catalyst and its reaction system are described.

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Arylation and aroylation reactions of unsaturated compounds, including alkenes and alkynes, catalyzed by transition metal complexes are powerful methods for preparing aromatic fine compounds. While the reactions with palladium catalysts are well documented and widely employed, those using rhodium species are less common. A number of unique and efficient rhodium-catalyzed reactions of several aromatic substrates, such as aroyl chlorides, aromatic acid anhydrides, arylboronic acids, arylstannanes, functionalized aromatic compounds, and aromatic aldehydes, with unsaturated compounds have, however, been developed in recent years. In this review are summarized the novel methods.

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Additions to C-C multiple bonds are simple and the most efficient methods in organic synthesis in terms of atom utilization due to avoidance of stoichiometric amounts of by-products. The following catalytic C-C, C-O and C-N bond-constructions by direct additions of nucleophiles to alkynes catalyzed by ruthenium complexes have been developed. 1) Dimerization of terminal alkynes to 1, 4-disubstituted butatriens which is an unusual tail-to-tail coupled product. 2) The first example of anti-Markovnikov hydration of terminal alkynes to aldehydes. 3) Intermolecular hydroamination of terminal alkynes with anilines to imines. Some of the reactions proceed in high yields under solvent-free, open-air conditions. Theoretical studies were also performed about transformation of η²-coordinated 1-alkynes to vinylidene complexes which plays important role in regioselectivity of the addition reactions.

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The chemistry of metallic samarium (Sm) is of current interest in organic synthesis. Though samarium iodide (SmI₂) is a good synthetic tool (a mild, neutral and ether-soluble one-electron reductant), its sensitivity to air makes it rather difficult to handle. We have been studying the reactivity of Sm to overcome this drawback of SmI₂. Dehalogenation of vic-dihalides with Sm gave alkenes and alkynes. These reductions were accelerated with a catalytic amount of acid. Olefinic double bonds of various α, β-unsaturated carboxylic acid derivatives (ester, amide, nitrile, carboxylic acid) were also reduced to give the corresponding 1, 4-reduction products. Aromatic carbonyl compounds were reduced to the corresponding pinacol coupling products with Sm-I₂ or Sm-I₂-Ti (OⁱPr) ₄ in methanol. Meso isomers were mainly produced in the presence of Ti (OⁱPr)₄ Acyl- or alkoxycarbonyl-protected alcohols or amides are deprotected easily and selectively under mild and neutral conditions. Stereoselective allylation and dimerization of optically active imines with Sm and a catalytic amount of I₂ have been successfully accomplished. Both Barbier-type allylation and intermolecular pinacol-like coupling reaction of imines were carried out smoothly to give allylation products and C₂-2, 2'-ethylenediiminodiethanol derivatives in a highly diastereoselective manner. This novel C₂-dimeric amino alcohols bearing primary alcohols catalyzed enantioselective addition of diethylzinc to aldehydes.

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[in Japanese]

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