Organocopper‐catalyzed living radical polymerization initiated with aromatic sulfonyl chlorides

The living radical polymerization of methyl methacrylate initiated from aromatic sulfonyl chlorides and catalyzed by the new catalytic systems CuSBu/bpy CuSPh/bpy and CuCCPh/bpy (bpy = 2,2′‐bipyridine) is described. For a target degree of polymerization of 200, lowering the ratio of catalyst to sulfonyl chloride group from 1/1 to 0.25/1 mol/mol decreases the values of the experimental rate constant of polymerization from 5.12 × 10⁻², 2.4 × 10⁻², and 1.87 × 10⁻² min⁻¹ to 1.8 × 10⁻³, 4.9 × 10⁻³, and 4.2 × 10⁻³ min⁻¹ for CuSBu, CuSPh, and CuCCPh, respectively, whereas the corresponding initiator efficiency increases from 62 to 99%. The external orders of reaction in the catalyst are 0.79 for CuSPh, 0.88 for CuCCPh, and 1.64 for CuSBu. A mechanistic interpretation that involves the in situ generation of, most likely, the real catalyst CuCl, starting from combinations of CuSBu, CuSPh, and CuCCPh and sulfonyl chloride or alkyl halide growing species, is suggested. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4353–4361, 2000     

Catalytic enantioselective borane reduction of aromatic ketones with sulfonyl (S)-prolinol

The asymmetric reduction of aromatic ketones was catalyzed by a class of recoverable and highly stable chiral sulfonamides derived from (S)-proline to yield optically active secondary alcohols in high yields and with enantiomeric excesses of up to 91%.     

Enantioselective borane reduction of aromatic ketones catalyzed by chiral aluminum alkoxides

The asymmetric borane reduction of prochiral ketones with an alkoxide catalyst prepared in situ from aluminum tri-iso-propoxide and (R)-binaphthol was examined. Using these conditions, alcohols were obtained in high yield and e.e.'s of up to 83%.     

The reduction of hexavalent tungsten

The reduction of WCl₆ in ethanol-acid medium by various metals was studied. Zinc dust gave complete reduction to the tetravalent state from which Zn or Zn + Fe could be removed by cellulose column chromatography or acetone-precipitation of WIV respectively. Attempts to prepare a WIV-oxine complex were unsuccessful     

Graphite catalyzed reduction of aromatic and aliphatic nitro compounds with hydrazine hydrate

Aromatic and aliphatic nitro compounds were readily reduced to amino compounds in excellant yields with graphite and hydrazine hydrate.     

Highly enantioselective reduction of beta,beta-disubstituted aromatic nitroalkenes catalyzed by Clostridium sporogenes

This is the first report of the use of Clostridium sporogenes extracts for enantioselective reduction of CC double bonds of beta,beta-disubstituted (1) and alpha,beta-disubstituted nitroalkenes (3). Crude enzyme preparations reduced aryl derivatives 1a-e and 1h, in 35-86% yield with > or =97% ee. Reduction of (E)- and (Z)-isomers of 1c gave the same enantiomer of 2c (> or =99% ee). In contrast, alpha,beta-disubstituted nitroalkene 3a was a poor substrate, yielding (S)- 4a in low yield (10-20%), and the ee (30-70% ee) depended on NADH concentration. An efficient synthesis of a library of nitroalkenes 1 is described.     

Oxidation of aromatic and aliphatic triisopropylsilanylsulfanyls to sulfonyl chlorides: preparation of sulfonamides

A series of aromatic and aliphatic triisopropylsilanylsulfanyls were prepared and oxidized to the sulfonyl chlorides with KNO₃/SO₂Cl₂. The sulfonyl chlorides were characterized via their conversion to sulfonamides.     

Lewis acid catalyzed sulfur transfer from a sultene to strained cyclic alkenes

[reaction: see text] Sultene 1 reacts with cyclic alkenes under mild Lewis acid catalysis to form thiiranes diastereoselectively. With 1-methoxycyclooctene as sulfur acceptor, an unexpected insertion product is formed, which provides valuable mechanistic insight into the sulfur-transfer process.     

手性含硫恶唑硼烷催化芳酮不对称还原反应的量子化学研究

用HF方法在6-31G^*基组下,对手性含硫恶唑硼烷催化苯乙酮不对称还原反应进行了量子化学从头算研究。还原反应经历了催化剂-硼烷加合物、催化剂-硼烷-酮加合物、催化剂-烷氧基硼烷加合物的生成以及催化剂-烷氧基硼烷加合物的离解过程。催化剂-硼烷加合物、催化剂-硼烷-酮加合物和催化剂-烷氧基硼烷加合物的生成分别为放热、吸热、放热过程;催化剂-烷氧基硼烷加合物离解成催化剂烷氧基硼烷为吸热过程。催化剂-硼烷-酮加合物和催化剂-烷氧基硼烷加合物都存在四种稳定的结构。最有利于氢转移的催化剂-硼烷-酮加合物结构是次低能量结构,并且具有扭曲的船形结构。催化剂-烷氧基硼烷加合物含有一个B-O-B-N四元环,尽管四元环有较大的张力,但加合物仍有较高的稳定性。     

Commutative reduction of aromatic ketones to arylmethylenes/alcohols by hypophosphites catalyzed by Pd/C under biphasic conditions

An efficient method is reported to reduce aromatic ketones selectively into arylmethylenes or alcohols with hypophosphites and Pd/C, depending on the selected conditions. This study could represent a promising alternative to the classical uses of standard hydrides or molecular hydrogen involved in reduction and deoxygenation procedures.     

Catalytic reduction of sulfuric acid to sulfur dioxide

The reduction of H₂SO₄ to SO₂ occurs with a relatively good efficiency only at high temperatures, in the presence of catalysts. Some experimental results, regarding conversion of sulfuric acid (96 wt.%) to sulfur dioxide and oxygen, are reported. The reduction has been performed at 800 ?C 900°C and atmospheric pressure, in a tubular quartz reactor. The following commercial catalysts were tested: Pd/Al₂O₃ (5 wt.% and 0.5 wt.% Pd), Pt/Al₂O₃ (0.1 wt.% Pt) and ??-Fe₂O₃. The fresh and spent catalysts were characterized by X-Ray diffraction and BET method. The highest catalytic activity was determined for 5 wt.% Pd/Al₂O₃, a conversion of 80% being obtained for 5 hours time on stream, at 9 mL h^?1 flow rate of 96 wt.% H₂SO₄. A conversion of 64% was determined for 0.5 wt.% Pd/Al₂O₃ and 0.1 wt.% Pt/Al₂O₃. For ??-Fe₂O₃, a less expensive catalyst, a conversion of 61% for about 60 hours was obtained.      

Polymerization of acrylic acid initiated by a hexavalent chromium-organic sulfur compounds reducing agent system

The kinetics of polymerization of acrylic acid initiated by Cr⁶⁺-thiourea, Cr⁶⁺-thioacetamide, Cr⁶⁺-2-aminoethane thiol, Cr⁶⁺-cysteine, and Cr⁶⁺-thioglycollic acid have been studied at 30, 35, and 40°C in nitrogen. The rates of polymerization were measured. Chromic acid alone did not initiate the polymerization under deaerated and un-deaerated conditions. On the basis of the experimental observation of the dependence of the rate of polymerization R_p on various variables, a suitable kinetic scheme is proposed.     

Polymerization of aromatic hydrocarbons with sulfur

The polymerization reactions of elemental sulfur with the polynuclear aromatic hydrocarbons pyrene and chrysene were studied. Heating the hydrocarbons with sulfur produces a series of sulfur-containing oligomers in which the aromatic ring systems remain intact. Polymerization is effected through the dehydrogenative action of sulfur and leads to thermally stable five- or six-membered heterocyclic ring systems. The major loss of sulfur during subsequent heat treatment occurs only at carbonization temperatures above 1000°C.     

Cerium catalyzed persulfate oxidation of polycyclic aromatic hydrocarbons to quinones

A practical synthesis of polycyclic quinones from the parent hydrocarbons is described. The twophase oxidation of hydrocarbons was accomplished by using ammonium persulfate in the catalytic presence of cerium ammonium sulfate, silver nitrate, and sodium dodecyl sulfate. The reaction conditions and scope have been discussed in detail.