Asymmetric synthesis of trans-2,3-disubstituted indoline derivatives

A novel method for asymmetric synthesis of trans-2,3-disubstituted indolines has been developed. The strategy involves the (-)-sparteine-mediated electrophilic substitution of 2-benzyl N-pivaloylaniline with aromatic or α,β-unsaturated aldehydes and subsequent intramolecular nucleophilic substitution. The simple protocol for two-step process can produce highly enantioenriched indolines 3a-o up to 98:2 er.     

One-pot catalytic asymmetric cascade synthesis of cycloheptane derivatives

A regiospecific, highly chemo-, diastereo-, and enantioselective one-pot catalytic cascade synthesis of cycloheptane derivatives is presented. In this chiral-amine-catalyzed asymmetric process, six new bonds and five new stereocenters were formed with excellent stereocontrol (>25:1 d.r. and 98- >99 ee).     

One-pot synthesis of tetrahydrofuran derivatives via a divalent palladium-catalyzed three-component coupling

Under divalent palladium catalysis, a three-component coupling reaction for synthesizing tetrahydrofuran derivatives has been established. The reaction involves the intramolecular carbopalladation of an alkyne with a carbanion which was generated from the addition of an alkoxide ion to an alkene derivative, followed by allylic chloride insertion to the CPd bond and quenching the CPd bond by β-heteroatom elimination in the presence of excess chloride ions.     

SmI2 mediated synthesis of 2,3-disubstituted indole derivatives

A novel preparation of 2,3-disubstituted indole derivatives was achieved through SmI₂ induced intramolecular reductive coupling reactions of acylamido carbonyl compounds.     

One-pot synthesis of enantiomerically enriched 2,3-disubstituted cyclopentanones via copper-catalyzed 1,4-reduction and alkylation

[reaction: see text]. Enantiomerically enriched 2,3-disubstituted cyclopentanones were prepared via copper-catalyzed 1,4-reduction of 3-substituted cyclopentenones followed by alkylation of the resulting silyl enol ether. Using this procedure, trans-2,3-disubstituted cyclopentanones were produced in moderate to good overall yields (42-67%) and with excellent enantiomeric and diastereomeric excesses. The reduction and alkylation were performed in a single reaction vessel.     

One-pot efficient green synthesis of 1,4-dihydro-quinoxaline-2,3-dione derivatives

An efficient synthesis of the potential pharmacophore 1,4-dihydro-quinoxaline-2,3-dione (1) has been achieved in a one-pot reaction at room temperature from substitutedo-phenylene diamine and oxalic acid under solvent-free conditions by a simple grinding method with unsurpassed atom economy. Thermal and powder X-ray diffraction analysis was carried out for some hydrated crystals.     

One-pot asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones catalyzed by amino acid-derived sulfonamides

An organocatalyzed approach to the asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones using amino-acid derived sulfonamides as organocatalysts, which can be easily prepared starting from l-proline, l-alanine, and l-phenylalanine, has been developed in high yields (up to 92%) and with moderate to good enantioselectivities (up to 74% ee). Additionally, opposite enantioselectivities for primary and secondary amino acid sulfonamides have also been observed.     

One-pot synthesis of 2-(dicyanomethylene)-1,2-dihydropyridine derivatives

The synthesis of 2-(dicyanomethylene)-1,2-dihydropyridine derivatives from the reactions of arylmethylidene derivatives of malononitrile dimers with 1,3-dicarbonyl compounds is described.     

One-pot synthesis of 3,4-disubstituted 1H-pyrroles from 2-tropanones

3,4-Disubstituted pyrroles (2, 3) were prepared from 6/7-carboxyethyl-3-phenyl-3-tropen-2-ones (1) regioselectively and with high yields by using tosylmethyl isocyanide (TosMIC). This procedure enables the synthesis of pyrroles substituted with two distinct groups: a phenyl group and a substituted pyrrolidine analogue. The crystal structure of product 2a was determined, and the analogous derivatives were identified by (1)H and (13)C NMR spectroscopy.     

One-pot synthesis of some 2H-Pyran-2-one derivatives

A one-pot synthesis of various 2H-pyran-2-one derivatives 5–19 starting from methyl ketones 1 , N,N-dimethylformamide dimethyl acetal and N-acylglycines 3 in acetic anhydride is described.     

A novel highly stereoselective synthesis of 2,3-disubstituted 3H-quinazoline-4-one derivatives

[structure: see text]. An efficient three-step synthesis of chiral 3H-quinazoline-4-one derivatives from commercial materials is disclosed. The Mumm reaction of imidoyl chloride with alpha-amino acids followed by reductive cyclization affords enantiomerically pure (ee >93%) quinazoline-4-ones in good overall yield. A comparison with existing approaches indicates that this method is superior for hindered substrates.     

螺羟吲哚类杂环衍生物的一锅法合成

在室温和水作溶剂条件下,阴离子交换树脂IRA-900有效催化含不同取代基的靛红、丙二腈和1,3-环己二酮,一锅法合成了12个相应的螺羟吲哚类杂环衍生物,其产率高达92%~99%.同时讨论了催化剂的种类、溶剂用量和催化剂的重复使用次数对反应的影响,并对IRA-900催化剂的反应机理进行了初步探讨.该方法具有条件温和,实验操作简单,以及催化剂能重复使用等优点,为螺羟吲哚类杂环衍生物提供了一条绿色合成方法.     

Nucleophilic addition to 2,3-disubstituted butanal derivatives and their application to natural product synthesis

The reaction of 2,3-anti-2-tert-butyldimethylsiloxy-3-substituted butanal derivative [anti-B, (±)-10 and (±)-16] derived from trans-(2,3)-epoxy butanoate (1) with carbon nucleophiles [α-furyl anion, acetate anion, and indium (In)-assisted allyl anion] has been investigated to give selectively the anti-, anti-adduct D. This anti-stereoselection could be explained by the Felkin-Anh transition state model. Thus obtained anti-, anti-adducts (±)-17 and (±)-38 were formally converted to natural products, (±)-asperlin (2) and (±)-olivose (4), respectively. The major anti-, anti-adduct (±)-26 was converted to (±)-digitoxose (3), while the minor anti-, syn-adduct (±)-27 was also converted to (±)-olivose (4). The reaction of (±)-10 with tert-butyl acetate anion gave predominantly afforded the anti-, anti-adduct (±)-23, which was converted to (±)-1,5-dideoxyhexitol (25). Alternately, the reaction of 2,3-syn-2-tert-butyldimethylsiloxy-3-p-methoxyphenoxy butanal derivative [syn-B, (±)-14] derived from trans-(2,3)-epoxy butanoate (1) with carbon nucleophile (In-assisted allyl anion) afforded a ca. 1 : 1 mixture of the syn-, anti-adduct E [(±)-32 or (±)-34] and syn-, syn-adduct F [(±)-33 or (±)-35]. After separation of this mixture, (±)-34 and (±)-35 were separately converted to (±)-oliose (5) and (±)-boivinose (6), respectively.     

Stereospecific synthesis of 2,3-disubstituted 1,4-benzodioxans

The synthesis of cis- and trans-2-methyl-3-phenyl-1,4-benzodioxans 4 and 5 , from 1-phenyl-2-[2-(hydroxy)-phenoxy]propanols threo 2 and erythro 3 are described.     

A new synthesis of 2,3-disubstituted indoles

A novel synthesis of 2,3-disubstituted indoles starting from N-alkyl-N-propvnyl anilines is described. The reactions employed are analogous to the thermal rearrangement of aryl propynyl sulfoxides.     

Stereocontrolled chemoenzymatic synthesis of 2,3-disubstituted piperidines

(R,R)-2,3-Disubstituted piperidines were readily synthesized starting from (R)-(+)-5-bromo-2-hydroxypentanenitrile (R)-2. An enantioselective (R)-oxynitrilase-catalyzed transcyanation was used to prepare the starting cyanohydrin (R)-2.     

One-pot synthesis of 1,4-disubstituted 1,2,3-triazoles from nitrobenzenes

A facile synthesis of 1,4-disubstituted 1,2,3-triazoles was achieved from nitrobenzenes and terminal alkynes under mild conditions. The reactions were successful for nitrobenzenes and terminal alkynes bearing various functionalities, from which the 1,2,3-triazole derivatives were smoothly synthesized through a four-step one-pot sequence.     

Divergent asymmetric synthesis of 3,5-disubstituted piperidines

A divergent synthesis of various 3,5-dioxygenated piperidines with interesting pharmacological properties is described. A mixture of the achiral cis- and racemic trans-3,5-piperidine diol could be efficiently obtained from N-benzylglycinate in five steps by the use of chemoenzymatic methods. In the subsequent enzyme- and Ru-catalyzed reaction, the rac/meso diol mixture was efficiently transformed to the cis-(3R,5S)-diacetate with excellent diastereoselectivity and in high yield. Further transformations of the cis-diacetate selectively delivered the cis-piperidine diol and the cis-(3R,5S)-hydroxy acetate. Alternatively, the DYKAT could be stopped at the monoacetate stage to give the trans-(3R,5R)-hydroxy acetate.