A carbon-carbon bond formation using an endoperoxide of N-methoxy-carbonylpyrrole and a convenient synthesis of 4-alkylindoles

A convenient synthesis of 4-alkylindoles was attained by utilizing the result of a stannous chloride-effected reaction of endoperoxide of N-methoxycarbonylpyrrole with carbon nucleophiles.     

Synthetic study of hetisine-type aconite alkaloids. Part 3: Total synthesis of (±)-nominine

Completion of the total synthesis of (±)-nominine (1) is described in detail. Based on the results of the preceding two papers, total synthesis of (±)-nominine was accomplished diverging from the intermediate 7. Thus, following pyrrolidine ring formation through transformation from 7 to 8, the C-ring was constructed by radical cyclization to form 10 from the enyne precursor 9. Subsequent elaboration of the C-ring, followed by formation of the azabicyclic ring system, completed a total synthesis of (±)-1. Single-crystal X-ray analysis of (±)-1 unambiguously confirmed its molecular structure and racemic crystal structure.     

Preparation and physical properties of amorphous V2O5 containing TiO2, Na2O or Li2O

V₂O₅ gels containing up to 18 mol% of TiO₂ were obtained through the simultaneous hydrolysis of alkoxides in ethanol solution. V₂O₅ gels containing Na₂O or Li₂O were obtained through the ion exchange method. The crystallization temperature, T_cr, of the gels increased and the H₂O content of the gels decreased by the addition of TiO₂ or Na₂O. These additives seem to stabilize the amorphous state of the gels. On the other hand, T_cr and the H₂O-content slightly varied with the addition of Li₂O. No ionic polarization was observed in coating films of the gels dried at temperatures below T_cr. The dc conductivity of the films was anisotropic, and increased with the addition of Li₂O or Na₂O. However, it decreased with increasing TiO₂ content. The fiber-like structure of gels was observed by TEM. The gels obtained from alkoxides were thin and short in comparison with the gels obtained through the ion exchange method.     

Palladium-catalyzed intramolecular α-arylation of aliphatic ketone, formyl, and nitro groups

Intramolecular arylation of properly designed substrates bearing a ketone, formyl, or nitro terminating group was achieved by use of a PdCl₂(Ph₃P)₂-Cs₂CO₃ reaction system to form a variety of carbocyclic compounds. Arylation in ketone compounds afforded benzene-annulated bridged or spirocycloalkanone derivatives, depending on the structure of the cyclization precursors. Arylation in formyl compounds occurred at the α-position (α-arylation) or at the carbonyl carbon (carbonyl-arylation) depending on the structure of the cyclization precursors and on the reaction solvent. An α-arylated secondary nitro group was partially transformed to ketone in the manner of the Nef reaction, whereas a tertiary nitro group was partially eliminated to afford a styrene-type olefin.     

Preparation of benzene, furan, and thiophene analogs of duocarmycin SA employing a newly-devised phenol-forming reaction

Five A-ring analogs of duocarmycin SA 9a-e were synthesized in racemic form modifying our second synthetic route toward duocarmycin SA. The problem encountered at the crucial phenol forming step to secure 17a, b from 16a, b under the conventionally used Kuwajima conditions was overcome by devising a more convenient method: simple heating of 16a-c in benzene in the presence of bis(triphenylphosphine)palladium(II) chloride (10 mol%), cesium carbonate (3 eq), and triphenylphosphine (0.3 eq) gave 17a-c in high yields of 86-91%. The intermediates 17a-e were readily led to the A-ring analogs (+/-)-9a-e almost according to the reported route.