Asymmetrische katalysen : XLVI. Enantioselektive Hydrosilylierung von Ketonen mit [Rh(COD)Cl]2 und optisch aktiven Stickstoff-Liganden

The synthesis and characterisation of 16 optically active nitrogen ligands, namely, pyridinethiazolidones, pyridinethiazolines, pyridinimidazolines, Schiff bases and bipyridines, are described. These ligands are used as cocatalysts together with the procatalyst [Rh(COD)Cl]₂ in the catalytic hydrosilylation of prochiral ketones with diphenylsilane. With these homogeneous in situ catalysts, optically active 1-phenylethanol is produced from acetophenone after hydrolysis of the silyl ether. The diastereomers of N-(1-phenylethyl)-2-(2-pyridinyl)-thiazolidine-4-one give opposite optical inductions. The best optical purity of 71.6% ee is obtained with a pinanyl-substituted bipyridine.     

铑(I)催化的不对称硅氢化反应合成手性2-氨基-1-芳基乙醇研究

报道了以Rh()-手性2-(2-吡啶基)-4-羧甲基-1,3-噻唑烷为催化剂,2-氨基芳香酮的不对称硅氢化反应,在常温常压下手性2-氨基-1-芳基乙醇的产率几乎可达定量,产品光学纯度可达80%e.e以上.     

聚甲基异丙烯基酮和聚异亚丙基丙酮的不对称硅氢化反应

光活性高分子的合成具有重要意义，它在生物活性高分子、用于不对称合成的高分子试剂或催化剂以及不对称选择性色谱柱填料等领域具有潜在的应用价值．研究表明，不对称选择性聚合反应难以获得高光学活性的高分子［１］，而手性过渡金属络合物催化的高分子不对称反应是获得...     

Rhodium(I) complexes of β-diketonates and related ligands as hydrosilylation catalysts

The complexes (O---O)Rh(CH₂CH₂)₂ ((O---OH) = FcC(O)CH₂C(O)CH₃, PhC(O)CH₂C(O)CH₃, 1,2-(CH₃CO)(OH)C₆H₄, 3-benzoyl-(+)-camphor) are catalysts for the hydrosilylation of PhMeCO with Ph₂SiH₂. The optical yield from the reaction catalyzed by the camphor derivative is too low to measure. Only low optical yields (max 8.7% e.e.) are obtained from the same reaction by using similar in situ catalysts with ligands prepared from (+)-PhCH(Me)NH₂. Bases such as H⁻ and PhCH(Me)NH⁻ catalyze the hydrosilylation reaction in the absence of rhodium salts, but only low optical yields are obtained. Ph₂SiH₂ reacts with 2-cyclohexen-1-one under these conditions and the mode of reaction depends on the reaction conditions.     

Asymmetric Synthesis of (R)-and (S)-Moprolol

A simple and effective procedure for the enantioselective synthesis of (R)-and (S)-moprolol was described.The key step was the asymmetric synthesis of enantiopure (R)-and (S)-guaifenesin,which were synthesized from enantioenriched (R)-3-chloro-1,2-propanediol and (S)-epichlorohydrin via kinetics of hydrolysis resolution of racemic epichlorohydrin by chiral Salen-CoIIII complex.The e.e.values of both the optical compounds were above 98%,and the chemical structures of the target compounds were confirmed by 1H NMR,13C NMR,IR,and MS.     

Asymmetric hydrosilylation of ketones catalysed by a chiral rhodium complex

Synthesis of optically active alkoxysilanes by asymmetric hydrosilylation of ketones, in the presence of a chiral phosphine—rhodium complex, is described; optical yields up to 46% are observed.     

手性2-(2-吡啶基)-4-羧乙基-1, 3-噻唑烷的合成及应用研究

以分级结晶和柱层析法对手性配体2-(2-吡啶基)-4-羧乙基-1,3-噻唑烷(A)进行了异构体分离提纯。将其与[Rh(COD)Cl]~2制备的原位催化剂用于催化苯乙酮及其它几种芳香酮的不对称硅氢化反应, 化学收率达90%左右, 光学纯度达80%e.e.左右, 噻唑烷环上的C~2构型对催化反应结果无影响, C~4位上酯基的影响也不大。     

Synthesis of isoxazoline N-oxides and its application in the formal synthesis of dehydroclausenamide

A protocol for the synthesis of isoxazoline N-oxides and its application in the formal synthesis of dehydroclausenamide are described. Sulfonium salt 1 reacts with substituted nitroalkenes smoothly to generate isoxazoline N-oxides in high to excellent yields with dr higher than 99/1. Its asymmetric version has been developed by using cinchona alkaloid-derived ammonium salts 6a and 6b instead of sulfonium salt 1 and higher than 96% ee values are achieved. This method has also been successfully applied to the formal synthesis of dehydroclausenamide.     

Asymmetric synthesis of quinolizidine alkaloids (−)-lasubine I, (−)-lasubine II and (+)-subcosine II

The enantioselective synthesis of (−)-lasubine I 1 and the first asymmetric synthesis of (−)-lasubine II 2 and (+)-subcosine II 3 is described. The key step is the intramolecular cyclization of N-acyliminium ion 4 which is derived from (S)-aminoester 6.     

手性2-(2-吡啶基)-4-羧乙基-1,3-噻唑烷的合成及应用研究

以分级结晶和柱层析法对手性配体2-(2-吡啶基)-4-羧乙基-1,3-噻唑烷(A)进行了异构体分离提纯。将其与[Rh(COD)Cl]_2制备的原位催化剂用于催化苯乙酮及其它几种芳香酮的不对称硅氢化反应,化学收率达90％左右,光学纯度达80％e.e.左右,噻唑烷环上的C_2构型对催化反应结果无影响,C_4位上酯基的影响也不大。     

手性2—（2—吡啶基）—4—甲酯基—1,3—噻唑烷的合成及应用

不对称氢化硅烷化可实现由含碳碳或碳杂双键的化合物合成手性醇和手性腹，在石油化工、药物合成、生物碱等生物活性物质的合成等领域具有潜在的应用价值．90年代以来，不断有高活性、高选择性的手性催化剂的开发研究报道［‘－‘］，使不对称硅氢化研究成为催化科学的一个研究方向．我们开展了带有毗吹取代基的座隆烷类手性络合催化剂的研究工作D·‘’．a一毗院甲醛、L一半就氨酸甲酯盐酸盐、氯化环辛M烯合＃［Rh（COD）CI」。以及Ph2SIH。按文献［7j制备，苯乙酮为分析纯试剂．所用仪器有SP－－2305型气相色谱仪，170SX－FTIR型…     

Asymmetric silyl nitronate cycloadditions with bornane-10,2-sultam derivatives

Asymmetric silyl nitronate cycloadditions with N-acryloyl (2R)-bornane-10,2-sultam, N-acryloyl (2S)-bornane-10,2-sultam, and N-methacryloyl (2R)-bornane-10,2-sultam have been studied. The asymmetric silyl nitronate cycloaddidon/elimination methodology provides a general route for the asymmetric synthesis of 2-isoxazolines.     

Asymmetric hydrosilylation of styrenes catalyzed by palladium-MOP complexes: ligand modification and mechanistic studies

In the palladium-catalyzed asymmetric hydrosilylation of styrene (3a) with trichlorosilane, several chiral monophosphine ligands, (R)-2-diarylphosphino-1,1'-binaphthyls (2a-g), were examined for their enantioselectivity. The highest enantioselectivity was observed in the reaction with (R)-2-bis[3,5-bis(trifluoromethyl)phenyl]phosphino-1,1'-binaphthyl (2g), which gave (S)-1-phenylethanol (5a) of 98% ee after oxidation of the hydrosilylation product, 1-phenyl-1-(trichlorosilyl)ethane (4a). The palladium complex of 2g also efficiently catalyzed the asymmetric hydrosilylation of substituted styrenes on the phenyl ring or at the beta position to give the corresponding chiral benzylic alcohols of over 96% ee. Deuterium-labeling studies on the hydrosilylation of regiospecifically deuterated styrene revealed that beta-hydrogen elimination from 1-phenylethyl(silyl)palladium intermediate is very fast compared with reductive elimination giving hydrosilylation product when ligand 2g is used. The reaction of o-allylstyrene (9) with trichlorosilane catalyzed by (R)-2g/Pd gave (1S,2R)-1-methyl-2-(trichlorosilylmethyl)indan (10) (91% ee) and (S)-1-(2-(propenyl)phenyl)-1-trichlorosilylethanes (11a and 11b) (95% ee). On the basis of their opposite configurations at the benzylic position, a rationale for the high enantioselectivity of ligand 2g is proposed.     

Preparation of optically active peralkyldiphosphines and their use, as the rhodium(I) complex, in the asymmetric catalytic hydrogenation of ketones

Two types of the optically active peralkyldiphosphine, 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(dialkylphosphino)butane (Rdiop 3) and N-(N′-substituted carbamoyl-4-dicyclohexylphosphino-2-dicyclohexylphosphinomethylpyrrolidine (R-Cycapp 8), have been prepared by various synthetic methods. Rhodium(I) complexes of 3 and 8 showed high catalytic activity for hydrogenation of various kinds of prochiral ketones, which were reduced smoothly to the corresponding optically active hydroxy compounds, under hydrogen at atmospheric pressure and ambient temperature. The neutral rhodium(I) complexes (diphosphine-Rh^N) hydrogenated -ketoamides and -ketopantolactone in fairly high optical yields (66–77%ee). In the hydrogenation of N-(-ketoacyl)--amino esters, the Cydiop-Rh^N catalyst showed a marked contrast to the diop-Rh^N system; in the hydrogenation of the methyl ester of N-(phenylglyoxyl)-(S)--phenylalanine, 72%de was attained with little double asymmetric induction by the chiral center in the substrate.     

噻唑烷类手性配体在不对称硅氢化反应中的应用(Ⅱ)

噻唑烷类手性配体在不对称硅氢化反应中的应用（Ⅱ）＊李弘姚金水何炳林（南开大学高分子化学研究所吸附与分离功能高分子材料国家重点实验室，天津３０００７１）关键词手性配体，铑络合物，噻唑烷，苯乙酮，不对称硅氢化自８０年代末期以来，合成了许多高活性、高选择性...     

New preparation of N(1)- and N(2)- alkylated tetrazoles via displacement of activated alcohols

A facile and convenient synthesis of N(1)- and N(2)-alkyltetrazoles is described. Tetrazole in the presence of zinc triflate reacts smoothly with activated alcohols to give the corresponding alkyltetrazole in high yield.     

β‐Ketoesters as Mono‐ or Bisnucleophiles: A Concise Enantioselective Total Synthesis of (−)‐Englerin A and B

A short enantioselective total synthesis of englerin A, a guaiane sesquiterpene with significant in vitro antitumor activity, is reported. Key features of this total synthesis are an organocatalytic asymmetric decarboxylative aldol reaction, a neighboring‐group‐participating [4+3] cycloaddition, a novel one‐pot Heck coupling/regioselective 1,4‐hydrosilylation/Tamao–Fleming oxidation cascade, and a kinetic CBS reduction, generating the optically pure natural product in 6.7 % overall yield over twelve steps starting from methylglyoxal. Selective saponification of the more reactive glycolic ester moiety of englerin A also gave (?)‐englerin B.     

Metal controlled enantioselectivity in the catalytic asymmetric hydrosilylation

The asymmetric hydrosilylation of acetophenone with Ph₂SiH₂ has been investigated in the presence of (S)-amphos as the chiral ligand in combination with the cyclooctadiene-rhodium(I), -iridium(I), -palladium(II), and -platinum(II) chloride complexes.

High activity and optical yields up to 50% ee have been obtained. The product configuration induced by the rhodium system is (S), in all other cases it was (R).     

Reduction of carbonyl compounds via hydrosilylation: V. Synthesis of optically active allylic alcohols via regioselective asymmetric hydrosilylation

Regioselective asymmetric reduction of prochiral α,β-unsaturated ketones to optically active allylic alcohols was performed via hydrosilylation catalyzed by a rhodium(I) complex with (+)-BMPP, (+)-DIOP and (?)-DIOP as chiral ligands. The allylic alcohols with optical purity up to 69% e.e. were obtained in good yields. The extent of asymmetric induction was found to depend on the stereo-electronic matching of the chiral ligand, ketone and hydrosilane employed. In the asymmetric reduction of (R)-carvone, leading to carveol, the extent of asymmetric induction was found to depend markedly on the ligand/rhodium ratio. Either trans-(5R,1S)-carveol or cis-(5R,1R)-carveol was obtained with good stereoselectivity by using (?)-DIOP or (+)-DIOP as chiral ligand, and it turned out that the chiral center present in carvone had only a slight influence on the asymmetric induction by the chiral catalysts.     

Homogeneous asymmetric catalysis by means of chiral metal complexes of 2,3-bis(dimenthylphosphino)maleic anhydride and of 2,3-bis(dimenthylphosphino)maleimide derivatives

2,3-Bis(dimenthylphosphino)maleic anhydride and also 2,3-bis(dimenthylphosphino)maleimide derivatives have been prepared from 2,3-dichloromaleic anhydride, 2,3-dichloro-N-phenylmaleimide and 2,3-dichloro-N-methylmaleimide, respectively, and dimenthyl(trimethylsilyl)phosphine. These compounds have been used as ligands for Rh complexes in the asymmetric hydrogenation and hydrosilylation. Ni and Pd complexes of these ligands were tested in the Grignard cross-coupling reaction.

The hydrogenation of -acetamido cinnamic acid gave 70% enantiomeric excess (ee) and hydrogenation of acetophenone up to 47% ee. Hydrosilylation of acetophenone led to 42% ee.

Attempts to asymmetric cross-coupling reactions resulted in very low enantiomeric excess.