Novel Method for the High-Yielding Synthesis of Steroidal Hydroxamic acid Derivatives

Steroidal 17-hydroxamic acid derivatives were synthesized in high yields in palladium-catalysed carbonylation reaction of 17-iodo-androst-16-ene derivatives under mild reaction conditions.     

Gold(I)-Catalyzed Bis-Cyclization of Allenynes for the Synthesis of Strained and Planar Polycyclic Compounds

A gold-catalyzed cascade cyclization of naphthalene-tethered allenynes gave strained fused phenanthrene derivatives. The reaction proceeds through the nucleophilic reaction of an alkyne with the activated allene to generate a vinyl cation intermediate, followed by arylation with a tethered naphthalene ring to form the 4H-cyclopenta[def]phenanthrene (CPP) scaffold. When using aryl-substituted substrates on the alkyne terminus, the gold-catalyzed reaction produced dibenzofluorene derivatives along with the CPP derivatives. Selective formation of CPP and dibenzofluorene derivatives depending on the reaction conditions is also presented.     

Ruthenium-catalyzed carbonylative cycloaddition of alpha-keto lactones with alkenes or alkynes: the participation of an ester-carbonyl group in cycloaddition reactions as the two-atom assembling unit

The reaction of benzofuran-2,3-dione derivatives 1 with CO and alkenes (or alkynes) results in a carbonylative [2+2+1] cycloaddition in which the ester-carbonyl group is incorporated into a two-atom assembling unit to give spirolactone derivatives 2. This reaction provides the first example of an ester-carbonyl group participating in a carbonylative cycloaddition reaction.     

A convenient procedure for the synthesis of fused fluoro isoquinolines

A base-promoted conversion of ortho-trifluoromethyl benzyl derivatives of NH-heterocycles into a respective fluorinated isoquinolines (38-57% isolated yields) is reported. The reaction is general for the benzylated derivatives of the electron-rich NH-heterocycles and the respective derivatives of pyrazole. The outcome of the reaction could be explained by an intermediate formation of a highly reactive quinone methide species.     

Practical synthesis of 2'-deoxy-4'-thioribonucleosides: substrates for the synthesis of 4'-thioDNA

We report herein a practical synthesis of 4'-thiothymidine (15) and appropriately protected 2'-deoxy-4'-thiocytidine (16), -thioadenosine (27), and -thioguanosine (29) derivatives, substrates for the synthesis of 4'-thioDNA, from the corresponding 4'-thioribonucleosides. 2'-deoxy-4'-thiopyrimidine nucleosides were synthesized using a radical reaction of the corresponding 2'-alpha-bromo derivatives, which were prepared via 2,2'-O-anhydro derivatives. 2'-deoxy-4'-thiopurine nucleosides were synthesized using the same radical reaction of the corresponding 2'-beta-bromo derivatives.     

固定化脯氨酸及其衍生物用于催化不对称有机合成

脯氨酸及其衍生物作为有机手性催化剂,在不对称有机合成中得到广泛应用。该类催化剂具有结构简单、来源丰富和选择性高等优点,但仍存在催化剂用量大、难以回收以及无法重复利用等不足。近年来,随着固定化技术的发展,固定化脯氨酸及其衍生物受到广泛关注。固定化脯氨酸及其衍生物催化剂可以简化不对称催化中产物的分离过程,实现催化剂的便利回收与循环使用。本文综述了固定化脯氨酸及其衍生物的制备及在催化不对称有机合成(如Aldol反应、Michael加成反应、Mannich反应等)中的研究进展。     

Mixed-bed polymeric o-nitrobenzophenone reagents for the on-line derivatization of amines in high performance liquid chromatography.

Several polymer-bound o-nitrobenzophenone reagents containing different detector-sensitive tags have been combined in the same reactor for the on-line derivatization of amine samples. The formation of multiple derivatives allows numerous opportunities for quantitation from the same injection, and also allows improved identification from the retention times of the multiple derivatives. Changing the reaction conditions changes the ratio of the products formed, so that changes in the ratio of peak heights and areas can also be used for analyte identification. In this work, propylamine was derivatized in acetonitrile on-line, precolumn. Changing the reaction conditions, of reaction time, temperature, solvent, presence of catalyst and the components of the reactor, changed the ratio of the derivatives formed. These changes in product formation with changing reaction conditions were applied to the identification and quantitation of amphetamine and methamphetamine in urine. The drugs were identified by the retention times of their derivatives, the ratio of the peak areas of the derivatives and the change in the ratios after changing reaction conditions. Each derivative was also used for quantitation of levels of spiked concentrations of amphetamine and methamphetamine, with relative errors less than 8%.     

A Study on the Ring Transformation of Dihydroisoxazolopyrimidine

Dihydroisoxazolopyrimidine derivatives could be cleaved to form either pyrimidine ring or isoxazole ring derivatives depending upon the reaction conditions employed.     

Diastereoselective Weitz-Scheffer epoxidation of levoglucosenone for the synthesis of isolevoglucosenone and derivatives

High-yielding epoxidation conditions for the cellulose pyrolysis product (?)-levoglucosenone (LGO) and 3-aryl derivatives of LGO have been developed. The reaction of LGO with hydrogen peroxide/base is known to give a Baeyer-Villiger reaction, however, it was found that the reactions of LGO or derivatives with tert-butylhydroperoxide/base affords solely epoxides through the Weitz-Scheffer reaction. A critical parameter in the successful isolation of the epoxide from LGO was to avoid all contact with water or alcohols during the reaction and workup. The epoxide products were reacted under Wharton conditions affording allylic alcohols and subsequent oxidation led to isolevoglucosenone or 3-arylisolevoglucosenone derivatives. Previously unreported reactions on isolevoglucosenone were then investigated.     

Generation and trapping of isobenzofuran intermediates formed in the coupling of Fischer carbene complexes and o-alkynylbenzoyl derivatives

[formula: see text] The coupling of o-alkynylbenzoyl derivatives with carbene complexes has been investigated. The reaction initially affords isobenzofuran derivatives, which convert to alkylidenephthalan derivatives or can be trapped by various dienophiles to afford benzo-oxanorbornene derivatives.     

The effect of substituents in the styryl moiety on the photocyclization of 4-styrylquinoline derivatives

The reaction of photocyclization and oxidation of 4-styrylquinoline and its derivatives with substituents in the p-position of the styryl moiety to the corresponding derivatives of benzo[i]phenantridine has been studied. It has been found that electron-donating substituents reduce the quantum yield of photocyclization under steady-state photolysis. Quantum-chemical calculations of the enthalpy of the cyclization reaction and analysis of the structure of the frontier molecular orbitals in the cis-isomer led to the conclusion that the observed effects relate to the influence of the substituents on both the photocyclization reaction proper and the thermal stability of dihydrobenzo[i]phenantridine derivatives as the primary products of photocyclization.     

A study of the reaction of N-chlorosuccinimide with indoles and its analytical application

The reaction of N-chlorosuccinimide with indole and few of its derivatives in acid medium has been studied. The purified products have been identified by TLC, elemental analysis and infrared studies, and a reaction mechanism is proposed on the basis of the results. The reaction proceeds smoothly and consistently, and can be used for microdetennination of indole and its derivatives.     

Reactions of CH acids with the Michael acceptors in the presence of potassium carbonate

Russian Chemical Bulletin - New 2-cyclohexenone derivatives were synthesized via the Michael reaction in the presence of potassium carbonate. These derivatives containing the acetyl substituent in...     

Theoretical study of the reaction mechanisms involved in the thermal intramolecular reactions of 1,6-fullerenynes

Substitution of a H atom by an alkyl group on the terminal carbon of the alkyne moiety of 1,6-fullerenynes has a strong impact on the products of the reaction undergone by this species after thermal treatment. While the reaction of 1,6-fullerenynes bearing an unsubstituted alkyne moiety results in the cycloaddition of the alkyne group to the fullerene double bond leading to cyclobutene-fused derivatives, the presence of an alkyl substituent leads to the formation of allenes. In the present work, we have performed an exhaustive theoretical analysis of all possible reaction mechanisms leading to cyclobutene-fused derivatives and allenes to offer an explanation of the reactivity differences observed. The results obtained show that formation of cyclobutene-fused derivatives occurs through a stepwise diradical reaction mechanism, while allene formation proceeds through a concerted way involving an uncommon intramolecular ene process. For the 1,6-fullerenynes bearing a substituted alkyne, the ene reaction path leading to allenes has an energy barrier somewhat lower than the stepwise diradical mechanism for the cyclobutene-fused derivative formation, thus explaining the outcome of the reaction.     

Synthesis of alkoxymethyl derivatives of resorcinarene via the Mannich reaction catalysed with iminodiacetic acid

The conditions of a simple synthesis of tetra(alkoxymethyl) derivatives of resorcinarene via the Mannich reaction catalysed with iminodiacetic acid are described. A possibility of high yield synthesis of such derivatives for the selected straight-chain alcohols is shown. A possible mechanism of this reaction is suggested.     

Studies on the chemistry of pharmacologically active heterocycles. Part I. Acid hydrolysis of hydrazino-1,2,4-triazine derivatives

The acid hydrolysis of 3-hydrazino-5,6-disubstituted-1,2,4-triazine, 3,5-dihydrazino-6-substituted-1,2,4-triazine, and 2-hydrazinopyrimidine derivatives was studied. It was found that the reaction proceeded through the formation of 3-keto and 3,5-diketo derivatives of the related 2,3-dihydro, 2,3,4,5-tetrahydro-1,2,4-triazines, and 2-keto derivatives of 1,2-dihydropyrimidines. It was concluded from these reactions that in 1,2,4-triazine derivatives the C-5 carbon is more reactive than the C-3 carbon toward nucleophiles. The reaction mechanism is discussed.     

Access to fused pyrroles via the reaction of spiro-dienyl ethers with amines involving a chemoselective skeletal rearrangement

Under metal-free conditions, the reaction of spiro-dienyl ethers, derived from furan derivatives, with aromatic amines provided fused pyrroles. The reaction proceeded through an interesting and chemoselective skeletal rearrangement and provided an alternative protocol for the construction of pyrrole rings from furan derivatives.     

Synthesis of ferrocenyl pyrazoles by the reaction of (2-formyl-1-chlorovinyl)ferrocene with hydrazines

Synthesis of ferrocenyl-substituted pyrazoles via the reaction between (2-formyl-1-chlorovinyl)ferrocene and hydrazine derivatives is described. Depending upon the substitution pattern of hydrazine, the reaction affords 1-alkyl/aryl-5-ferrocenylpyrazoles and/or 1-alkyl/aryl-3-ferrocenylpyrazoles. The reaction appears to be general for a variety of hydrazine derivatives.     

Facile and efficient synthesis of lactols by a domino reaction of 2,3-epoxy alcohols with a hypervalent iodine(III) reagent and its application to the synthesis of lactones and the asymmetric synthesis of (+)-tanikolide

The domino reaction of 2,3-epoxy-1-alcohol derivatives, namely tetrasubstituted 2,3-epoxy-1-alcohols and 2- or 3-alkyl trisubstituted 2,3-epoxy-1-alcohols, with PhI(OCOCF(3))(2) in the presence of H(2)O is described in detail. In this reaction, several types of lactol derivatives can be directly obtained from the 2,3-epoxy-1-alcohol derivatives in a single operation. The obtained lactols were successively converted into the corresponding lactones. This reaction is applicable to the construction of optically active lactone compounds. The asymmetric total synthesis of (+)-tanikolide, an antifungal marine natural product, has been effectively achieved by using this reaction.     

Catalytic activation of the leaving group in the S(N)2 reaction

A novel catalytic activation of the leaving group in the S(N)2 reaction is achieved as an extension of our mercuric triflate-catalyzed reactions. Derivatives of anilinoethyl 4-pentynoate reacted smoothly with catalytic amounts of Hg(OTf)(2) to give indoline derivatives in excellent yield with efficient catalytic turnovers under very mild conditions. The reaction of optically pure secondary alcohol derivatives resulted in inversion of stereochemistry, which is a definitive feature of the S(N)2 reaction. The procedure is applicable for benzoazepine synthesis.