First synthesis of Estrogen-Imidazolium Cyclophanes

A series estrogen-imidazolium cyclophanes have been synthesized for the first time by direct quaternization of 2,4-bis(N-imidazolylmethyl)estrogens and corresponding dibromides in highly diluted acetonitrile solution in excellent yields. All new compounds were characterized by MS, 'HNMR and elemental analysis.     

Reprint of: Acid-mediated four-component tandem cyclization: Access to multifused 1,3-benzoxazine frameworks

An acid-mediated multicomponent reaction has been developed for the direct synthesis of multifused 1,3-benzoxazine derivatives from simple and readily available arylglyoxal monohydrates and 2-aminobenzyl alcohols under mild conditions. This novel protocol is proposed to proceed through intramolecular poly-heterocyclizations, thus leading to the formation of three new rings and six new chemical bonds, including four CN and two CO bonds.     

Novel heterocyclic systems. Synthesis of 2,7-dimethyl-10-oxa-1,8-diaza-anthracen-9-one and derivatives

Synthesis of novel heterocycles, which contain the unique 10-oxa-1,8-diazaanthracen-9-one tricyclic core, is reported. The core structure was assembled via a dehydrative-cyclization strategy.     

3-取代-6-甲氧基-7-羟基-4Н-色烯-4-酮的合成及其异常反应

报道了3-位分别为苯基、氢原子以及卤素等不同取代的4Н-色烯-4-酮类化合物的合成方法,并探讨和阐明了一些意外产物的获得机理,不仅对该位点的进一步结构改造提供了物质基础,同时拓展了构建4Н-色烯-4-酮类化合物的底物结构.     

N-苯基和N-乙氧羰基甲基磷异喹啉酮及其衍生物的合成

以邻炔基苯磷酰胺为原料经Pd(II)催化的环化反应、环化偶联反应和氯环化反应高收率合成了15个N-苯基和N-乙氧羰基甲基磷异喹啉酮及其4-烯丙基、4-氯衍生物, 它们的结构均经过1H NMR, 13C NMR, MS, IR及元素分析确证.     

Aryl radical cyclizations of N-(2-halobenzoyl)-cyclic ketene-N,S-acetals

2-Ethylthiazolines react with 2-halobenzoyl chlorides to form N-(2-halobenzoyl)-cyclic ketene-N,S-acetals, which undergo stereo-controlled radical cyclizations to afford (R,S,S)-3-alkyl-10-methyl-2,3,10,10a-tetrahydrothiazolo[3,2-b]isoquinolin-5-one and (R,R,S)-3-alkyl-10-methyl-2,3,10,10a-tetrahydrothiazolo[3,2-b]isoquinolin-5-one.     

Nickel-catalyzed reductive cyclizations and couplings

For over 50 years, nickel catalysis has been applied in cycloaddition processes. Nickel-catalyzed reductive couplings and cyclizations, however, have only recently attracted a high level of interest. This group of new reactions allows a broad range of multicomponent couplings involving two or more pi components with a main-group or transition-metal reagent. These processes allow the assembly of important organic substructures from widely available reaction components. Multiple contiguous stereocenters, polycyclic ring systems, and novel arrays of complex functionality may often be prepared from simple, achiral, acyclic precursors. With three or more reactive functional groups participating in the catalytic processes, many mechanistic questions abound, including the precise timing of bond constructions and the nature of reactive intermediates. This Review is thus aimed at providing a critical evaluation of recent progress in this rapidly developing field.     

Regioselective Synthesis of 2-Trimethylsilyl-4H-pyran-4-ones from 1-Ethoxy(hydroxy)-5-(trimethylsilyl)pentenynones

Exclusive formation of 5-aryl-2-trimethylsilyl-4H-pyran-4-ones is accomplished by a regioselective cyclization of 2-aryl-1-ethoxy(hydroxy)-5-(trimethylsilyl)pent-1-en-4-yn-3-ones. This cyclization occurs in a 6-endo-dig mode through addition to the β-atom of the TMS substituted triple bond. The reaction was found to be general for a range of ethoxyenynones upon heating in glacial acetic acid and for analogous hydroxyenynones in diphenyl ether. Plausible mechanistic explanation and possible post-modifications of resulting pyranones are offered.     

Visible-light induced cascade radical cyclization of sulfinic acids and o-(allyloxy)arylaldehydes towards functionalized chroman-4-ones

An efficient method for the synthesis of functionalized chroman-4-ones induced by visible light via the radical cyclization reaction of sulfinic acids and o-(allyloxy)arylaldehydes at room temperature was described. The corresponding products were isolated with moderate to good yields. Radical mechanism was proposed for this transformation. Anti-microbial activity of some desired compounds were screened.     

α-叔戊酰基硫代甲酰胺缩氨基脲环化反应

含1,2,4-三嗪结构的化合物具有抗病毒、调节植物生长等作用。本文用α-叔戊酰基硫代甲酰取代苯胺缩氨基脲环化得到4-取代苯基-6．叔丁基-5-硫酮-1,2,4三嗪-3-酮,进一步环化得到5诹代苯氨基-6-叔丁基-1,2,4-三嗪-3-酮。反应方程式如下：     

Ruthenium‐catalyzed cyclizations of enynes via a ruthenacyclopentene intermediate: Development of three novel cyclizations controlled by a substituent on alkyne of enyne

Three novel ruthenium‐catalyzed cyclizations of enynes were developed. In each cyclization, a ruthenacyclopentene derived from enyne and Cp*RuCl(cod) is a common intermediate. When an enyne having an alkyl, an ester, or a formyl group on an alkyne was reacted with Cp*RuCl(cod) under ethylene gas, ethylene was inserted into the ruthenium‐sp² carbon bond of ruthenacyclopentene to afford ruthenacycloheptene, and β‐hydrogen elimination followed by reductive elimination occurred to give a cyclic compound having a 1,3‐diene moiety. When an acyl group was placed on the alkyne, the carbonyl oxygen coordinated to the ruthenium metal of ruthenacyclopentene to produce a ruthenium carbene complex, which reacted with ethylene to give a cyclic compound having a cyclopropane ring on the substituent. On the other hand, when the substituent on the alkyne was pent‐4‐enyl, insertion of an alkene part into ruthenacyclopentene followed by reductive elimination gave a tricyclic compound by a ruthenium‐catalyzed [2 + 2 + 2] cyclization of diene and an alkyne. DOI 10.1002/tcr.201100003     

Formal alkylation of allenes through highly selective radical cyclizations of allene-enes

Something radical: the first example of alkene-to-allene radical cyclization of allene-enes is reported. The highly chemoselective intermolecular radical addition reaction of the alkene and subsequent, exclusive exo-radical addition to the allene was realized with perfluoroalkyl radicals. A subsequent TBAF-promoted dehydroiodination of the cyclization products forms cyclopentanes and regenerates an allene moiety (TBAF=tetra-n-butylammonium fluoride).     

The synthesis of carbohydrate-derived acylsilanes and their intramolecular free radical cyclizations with the formation of polyoxygenated cyclopentanes

A convenient way for the synthesis of acylsilanes from arabinose, lyxose, and ribose is developed. All the chiral centers of the carbohydrate templates are conserved, and only the reducing end is transformed into the acylsilane functional group. The non-reducing end of the templates can be converted into a bromide. These bromo acylsilanes undergo efficient intramolecular radical cyclizations to give polyoxygenated cyclopentanes.     

An efficient synthesis of novel chromeno[3’, 4’：5, 6]pyrano[2, 3-b]indole derivatives

An efficient two-step method was described for the synthesis of chromeno[3',4':5,6]pyrano[2,3-b]indole derivatives. The three-component reaction of 4-hydroxycoumarin, variously substituted benzaldehydes and indolin-2-one was promoted by P2O5 in refluxing ethanol to give trimolecular adducts, which were then cyclized in 1,2-dichloroethane under reflux using POCl3.     

Reaction of enol ethers with alkynes catalyzed by transition metals: 5-exo-dig versus 6-endo-dig cyclizations via cyclopropyl platinum or gold carbene complexes

The intramolecular reaction of enol ethers with alkynes in methanol is catalyzed by electrophilic Pt(II), Pd(II), and Au(III) chlorides and by a Cu(I) complex to give five- or six-membered rings bearing dimethyl acetals. The reaction takes place by an anti addition of the enol ether and the metal to the alkyne. The possible involvement of vinylidene complexes in this reaction is excluded. In addition to the usual 5-exo-dig (or 6-exo-dig) pathways, a 6-endo-dig pathway has also been found to take place with certain enynes. One case of 5-endo-dig cyclization has also been found. A general scheme for the alkoxycyclization of enynes catalyzed by transition metals based on DFT calculation of PtCl(2) and AuCl(3) complexes that includes exo and endo cyclizations is presented.     

Enhanced reactivity in radical cyclizations of hydrazones using the silicon-tethered 1-bromovinyl group

A silicon-tethered 1-bromovinyl group was shown to function as a radical precursor for tin-mediated vinyl additions to chiral α- or β-hydroxyhydrazone. In contrast to related thiyl-mediated methods, these vinyl bromides were not limited to the 5-exo cyclization mode. A series of Si-tethered 5-exo and 6-exo cyclizations formed the corresponding five- and six-membered exo-methylene-substituted oxasilacycles. Treatment with fluoride cleaved the Si-C and Si-O bonds to afford the corresponding allylic hydrazines. Diastereoselectivities ranged from 2:1 to 25:1 (anti:syn) for the 5-exo cyclizations, depending on the size of the exocyclic substituent, but 6-exo cyclization was not diastereoselective. A variant involving Tamao oxidation of the exo-methylene oxasilacyclopentane intermediate afforded a methyl ketone, a net process corresponding to addition of a radical acyl anion equivalent.