Asymmetric acylation of carboxamides having trans-2,5-bis(methoxymethoxymethyl)pyrrolidine moiety as a chiral auxiliary and stereoselective reduction of the resulting 2-alkyl-3-oxoamides

$\text{trans}$-2,5-Bis(methoxymethoxymethyl)pyrrolidine proved to be an excellent chiral auxiliary for the asymmetric acylation of the corresponding carboxamide enolates and the stereoselective Zn(BH₄)₂ reduction of the resulting 2-alkyl-3-oxo amides provided a useful alternative to asymmetric aldol reaction.     

Bis((2-methoxymethyl)pyrrolidine)phosphine as effective chiral auxiliary for the stereoselective synthesis of chiral ferrocenyl diphosphines

The bis(2-methoxymethyl pyrrolidine)phosphine moiety is shown to be a very effective chiral auxiliary for the ortho- and diastereoselective lithiation of ferrocene, thereby allowing the highly selective attachment of various electrophiles to the cyclopentadienyl ring of ferrocene. The potential of the methodology is demonstrated by the synthesis of Kephos, a new family of ferrocenyl diphosphines and of OH-Taniaphos derivatives.     

Asymmetric synthesis of sulfinamides using (-)-quinine as chiral auxiliary

A process has been designed and demonstrated for the asymmetric synthesis of sulfinamides using quinine as auxiliary. A variety of chiral sulfinamides including N-alkyl sulfinamides with diverse structure were prepared in good yields and excellent enantioselectivity starting from easily available and inexpensive reagents. The auxiliary quinine could be recovered and recycled.     

Asymmetric aldol reactions using chiral CF3-Oxazolidines (Fox) as chiral auxiliary

The aldol reactions of amide enolates derived from a trifluoromethylated oxazolidine (Fox) chiral auxiliary occur in good yields with a moderate anti diastereoselectivity (Li and Na enolates) to a high syn diastereoselectivity (boron enolate). After removal, the Fox chiral auxiliary is very conveniently and efficiently recovered in basic conditions.     

Synthesis of chiral 2-(anilinophenylmethyl)pyrrolidines and 2-(anilinodiphenylmethyl)pyrrolidine and their application to enantioselective borane reduction of prochiral ketones as chiral catalysts

Chiral diamines, 2-(anilinophenylmethyl)pyrrolidines and 2-(anilinodiphenylmethyl)pyrrolidine, were prepared from N-(tert-butoxycarbonyl)pyrrolidine or (S)-proline as a starting material, respectively. These chiral diamines were efficient for the catalytic enantioselective borane reduction of acetophenone. Using (S)-2-(anilinodiphenylmethyl)pyrrolidine, chiral secondary alcohols were obtained from prochiral ketones with good to excellent enantiomeric excesses (up to 98% ee).     

Synthesis of chiral 1-(imidazol-2-yl)alkanamines using neomenthanethiol as a chiral auxiliary

Diastereomeric N-(imidazol-2-ylmethylidene)neomenthane-3-sulfinamides were obtained from enantiomerically pure neomenthanethiol in three steps. The compounds obtained added Grignard reagents at the C=N bond. After separation of diastereomers, an acid resolution gave enantiomerically pure primary 1-(imidazol-2-yl)alkanamines. In this scheme, the neomenthane fragment played the role of a chiral auxiliary.     

Synthesis and characterization of new polyhydrazides based on 2,5-bis(mercapto-acetichydrazide)-1,3,4-thiadiazole moiety

New interesting class of novel polyhydrazides containing 1,3,4-thiadiazole moieties in the main chain was synthesized. A solution polycondensation technique was used in the synthesis of these polymers. The new monomer namely: 2,5-bis(mercapto-acetichydrazide)-1,3,4-thiadiazole III was synthesized from the nucleophilic replacement of 2,5-dimercapto-1,3,5-thiadiazole I with ethylchloroacetate, followed by hydrazinolysis. The model compound VII was synthesized from the monomer 2,5-bis(mercapto-acetichydrazide)-1,3,4-thiadiazole III with benzoyl chloride and characterized by ¹H- NMR, IR, and elemental analyses. The polyhydrazides were synthesized from the polymerization of monomer III with 4,4^′-biphenic, 3,3^′-azodibenzoyl, 4,4^′-azodibenzoyl dichlorides. These polymers were characterized by elemental and spectral analyses, viscometry and solubility. The thermal properties of these polymers were determined by thermal gravimetric analyses, and differential thermal analysis, and correlated with their structure. The crystallinity of some polymers was tested by X-ray analyses.     

Synthesis and reduction of 5,5-dimethyl-2,4-bis(3,4-dimethoxyphenyl)-2-chloro-2,5-dihydrofuran

A new, stable 5-membered ring heterocyclic cation was prepared and reduced into the corresponding dihydrofuran, tetrahydrofuran and pentanol derivatives.     

Crystal structure of 2-p-anisidino-2,5-bis (trifluoromethyl)-3-perfluoroisobutenyl-5-monohydroperfluoro-3-hexene

Conclusions The structure of 2-p-anisidino-2,5-bis(trifluoromethyl)-3-perfluoroisobutenyl-5-monohydroperfluoro-3-hexene has been determined by x-ray diffraction analysis, proving the occurrence of the 1,4-addition of nucleophiles to a cross-conjugated perfluorotriene.Translated from Izvestiya.Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 588–592, March, 1981.     

Synthesis and crystal structure of a novel chiral compound prepared from (-)-borneol as a natural chiral auxiliary

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Asymmetric total synthesis of (20S)-Camptothecin using a chiral auxiliary strategy

An asymmetric eight-step total synthesis of (20S)-camptothecin, starting from the known compound tert-butyl (2-chloroquinolin-3-yl)methylcarbamate, is described. A Heck reaction followed by an intramolecular Michael addition to form the C-ring provides the first key step in this synthesis. The construction of the 20(S) chiral center relies on a chiral auxiliary-mediated Michael addition using (2R,5R)-2-tert-butyl-5-ethyl-1,3-dioxolan-4-one as the auxiliary.     

1-(2-螺二芴)-3,4-二[3-(2,5-二甲基呋喃)-2,5-二氢吡咯的合成及光致变色性质的研究

将螺二芴引入二芳基乙烯分子中,设计合成了一种新型的含螺二芴呋喃芳香杂环的二芳基乙烯光致变色分子7a.用FT-IR,NMR,MS和元素分析进行结构表征;研究了7a在正己烷溶液和乙腈溶液中的光致变色反应,结果表明7a在两种溶剂中均具有良好的光致变色性能.并且7a在正己烷溶液中变色速率和转化率比在乙腈溶液中大.还研究了7a光致变色过程中荧光光谱的变化,发现关环反应后荧光被淬灭,并且7a的荧光发射峰在极性溶剂中有很大的蓝移.研究了开环态7a,关环态7b的热稳定性,发现7a的热失重温度比未用螺二芴修饰的8a提高了100℃.7b的热稳定性也比8b高.     

Asymmetric synthesis of trans-2,5-disubstituted pyrrolidines from enantiopure homoallylic amines. Synthesis of pyrrolidine (-)-197B

Iodocyclization of sulfinimine-derived enantiopure homoallylic sulfonamides affords trans-2,5-disubstituted 3-iodopyrrolidines and represents valuable methodology for the asymmetric synthesis of this important heterocyclic ring system.     

Asymmetric synthesis of methyl bacteriopheophorbide-d and analogues by stereoselective reduction of the 3-acetyl to the 3-(1-hydroxyethyl) group

Asymmetric borane-reduction of 3-acetyl-13¹-oxo-tetrapyrroles (=bacteriochlorin, chlorin and porphyrin) in the presence of a chiral source gave selectively chiral 3-(1-hydroxyethyl)-13¹-oxo-tetrapyrroles. Oxazaborolidines were effective as chiral auxiliaries. Reduction with (S)-oxazaborolidines led to the (3¹S)-alcohol as the major product, whose stereoselectivity was the opposite of that in the same asymmetric reduction of usual prochiral ketones ArCOR. The asymmetric reduction of the 3-acetyl group in methyl bacteriopyropheophorbide-a and the 7,8-oxidation afforded 3¹-epimeric methyl (3¹S)-bacteriopheophorbide-d (89% de).     

Synthesis of (S,S)-1,5-bis(4-alkyl-5-hydroxy-2-oxo-3-azapentyl)-1,5-diazacyclooctane

Crown ether derivatives have been extensively developed to provide enhanced structural recognition of substrate alkyl-ammonium cations. In particular a number of investigations of complexation of chiral alkylammonium salts by chiral crown ethers have been reported. The enantioselectivity has been applied in the chromatographic resolution of amino acid perchlorates. In general the crown ethers used in these studies have been based upon derivatives of 2, 2′-dihydroxy-1, 1′-binaphthyl1 or deriv…