Kin-ya Akiba

Regioselective synthesis of 4-alkylpyridines via 1,4-dihydropyridine derivatives from pyridine

Abstract N-Ethoxycarbonylpyridinium chloride ( 1 ) reacted with RCu·BF 3 at 4-position with almost complete regioselectivity (better than 99%) to afford the corresponding 1,4-dihydropyridine derivatives ( 2 ) in high yields (81≈94%). The dihydropyridines were readily oxidized by oxygen to give 4-alkylpyridines ( 4 : 38≈68% yields).

Metallic bismuth mediated allylation of aldehydes to homoallylic alcohols

Abstract In the presence of metallic bismuth, allyl halides were found to react with aldehydes under mild conditions to give the corresponding homoallylic alcohols in good yields.

Regioselective synthesis of 4-(2-oxoalkyl)pyridines via 1,4-dihydro-pyridine derivatives using silyl enol ethers and pyridinium salts

Abstract Trimethylsilyl enol ethers ( 1 ) reacted with 1-ethoxycarbonylpyridinium chloride ( 3 ) at 4-position with high regioselectivity to afford 1-ethoxycarbonyl-4-(2-oxoalkyl)-1,4-dihydropyridines ( 4 in 42 – 87% yields. When 2, 2, 2-trichloroethyl chloroformate was employed, yields of the corresponding 1,4-dihydropyridines ( 8 0 were higher (80 – 100% yields). 4 and 8 were oxidized by oxygen or AgNO 3 to give 4-(2-oxoalkyl)pyridines ( 12 : 30 –65%).

Carbon-carbon bond formation with bismuth salt: a chemoselective Grignard-type addition of allyl unit to aldehydes

Abstract In the presence of bismuth(III) chloride—metallic zinc or bismuth(III) chloride—metallic iron, allylic halides were found to react with aldehydes under mild conditions to give the corresponding homoallylic alcohols in high yields with high chemoselectivity.

Bismuth trichloride as a new efficient catalyst in the aldol reaction

Abstract In the presence of a catalytic amount of bismuth trichloride (5 mol%), silyl enol ethers react with aldehydes at room temperature to give the corresponding aldols in good yields.

Synthesis and structure of a hexacoordinate carbon compound

In an exploration of six coordination and hypervalence in carbon compounds, steric constraints have been employed to bring four ether O atoms in close proximity to an allenic carbon atom. The dimethylated dication 2 is confirmed to have hexacoordinate carbon by experimental charge density analysis and DFT calculations and is arguably hypervalent.

Addition of boron trifluoride complexes of organocopper reagentsto aldimines containing α-hydrogens

Abstract RCu · BF 3 , generated in situ from Grignard reagents, CuI, and BF 3 · OEt 2 , added to aldimines containing α-hydrogens to afford secondary amines in good yields. Boron trifluoride complex of dialkylcuprate gave essentially the same result with wider application.

Synthesis and chemical behaviors of 12-substituted dibenz[c,f][1,5]azastibocine and dibenz[c,f][1,5]azabismocine derivatives: evidences of 10-Pn-4 type hypervalent interaction

Abstract A series of 12-substituted 6-methyl-5,6,7,12-tetrahydro-12-X-dibenz[c,f][1,5]azastibocine (1) and azabismocine (2) were prepared. Both 1 H and 13 C NMR signals of the N-methyl group were shifted to downfield by electron-withdrawing substituent at the pnictogen atoms and the shift was linearly correlated with Hammett σ m values.

Synthesis, Reactions, and Electronic Properties of 16 π-Electron Octaisobutyltetraphenylporphyrin

The reaction of the doubly oxidized beta-octaisobutyl-meso-tetraphenylporphyrin (OiBTPP, 4), which has a 16 pi-electronic structure at the porphyrin core, with a variety of metal reagents was investigated. The reaction of 4 with SnCl(2) followed by ethanolysis afforded an 18 pi-electron tin complex, (OiBTPP)Sn(OEt)(2) (5), in a redox manner. No reactions were observed using zerovalent metals (Zn, Cu, and Pd). However, the reaction of 16pi [(OiBTPP)Li](+)[BF(4)](-) (6), which was easily derived from 4, with Zn, Cu, and Pd(2)(dba)(3) gave the corresponding 18pi metalloporphyrins (OiBTPP)M (7, M = Zn(EtOH); 8, M = Cu; and 9, M = Pd). One-electron oxidation of the copper complex 8 by AgSbF(6) afforded a 17 pi-electron cation radical complex, [(OiBTPP)Cu](*+)[SbF(6)](-) (10). The UV-visible and electron spin resonance spectra of 10 were quite similar to those of previously reported beta-octaethyl-meso-tetraphenylporphyrin (OETPP) derivatives, [(OETPP)Cu](*+)X(-) (X = ClO(4), I). In contrast to the reaction of 6 with Zn to give the 18pi complex 7, the reaction of 4 with divalent ZnCl(2) enabled us to isolate a new 16pi porphyrin-zinc(II) complex, [(OiBTPP)Zn(Cl)](+)[ZnCl(3)](-) (11), in 92% yield. The solid-state structures of 5 and 7-11 were unambiguously determined by single-crystal X-ray crystallography. The porphyrin cores of 10 (17pi) and 11 (16pi) are much more distorted than those of the 18pi derivatives 5 and 7-9. Furthermore, the bond distances of 10 and 11 clearly showed the presence of bond alternation in contrast to aromatic 18pi species 8 and 7, respectively. Nucleus-independent chemical shift calculations of 4 and some metalated porphyrins indicated that the highly distorted 16pi porphyrins are essentially nonaromatic, with only weak antiaromaticity. Magnetic circular dichroism studies in conjunction with ZINDO/S calculations assisted in identifying the electronic transitions of the UV-vis spectra of key porphyrins. Electrochemical and thin-layer UV-vis spectroelectrochemical experiments on 4 (16pi) and 11 (16pi) indicated that both compounds can be electroreduced to give the 18pi species, with the 16pi/18pi transition being reversible in the case of [(OiBTPP)Zn(Cl)](+)[ZnCl(3)](-) (11).

Facile synthesis of 4-substituted pyridines using grignard reagents

Abstract N-t-Butyldimethylsilylpyridinium triflate 2 reacted with Grignard reagents at 4-position with almost complete regioselectivity ( > 99%) to afford the corresponding 1,4-dihydropyridine derivatives ( 3 ), which are easily oxidized by oxygen to give 4-substituted pyridines ( 4 : 58 – 70%).