A bidirectional access to novel thiadiazine hybrid molecules by double multicomponent reactions

In an attempt to further exploit multicomponent reactions in the field of hybrid heterocyclic molecules, we describe a bidirectional approach for the synthesis of novel 1,3,5-thiadiazine-peptides molecules. The process relies on the execution of two Ugi reactions between dicarboxy-functionalized 1,3,5-thiadiazine with different amines and isocyanides. An alternative strategy relying on a sequential multicomponent macrocyclization procedure was also developed to afford thiadiazine peptide-like macrocycles. Both methods showed great chemical efficiency and versatility.     

Sequential regio and chemoselective cross-coupling reactions by means of O-tri-isopropylsulfonate of 4-bromo-pyridazine 3,6-dione

Regioselective desymmetrization of 4-substituted pyridazin-3,6-diones using sterically hindered 2,4,6-triisopropylphenyl-sulfonylchloride allowed efficient sequential palladium cross-coupling reactions.     

Postfunctionalization of polyoxanorbornene via sequential Michael addition and radical thiol‐ene click reactions

We demonstrated the successful postfunctionalization of poly(oxanorbornene imide) (PONB) with two types of double bonds using sequential orthogonal reactions, nucleophilic thiol‐ene coupling via Michael addition and radical thiol‐ene click reactions. First, the synthesis of PONB with side chain acrylate groups is carried out via ring‐opening metathesis polymerization and nitroxide radical coupling reaction, respectively. Subsequently, the resulting polymer having two different orthogonal functionalities, main chain vinyl and side chain acrylate, is selectively modified via two sequential thiol‐ene click reactions, nucleophilic thiol‐ene coupling via Michael addition and photoinduced radical thiol‐ene. The orthogonal reactivity of two diverse double bonds, vinyl and acrylate functionalities, for the abovementioned consecutive thiol‐ene click reactions was first demonstrated on the model compound. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Cobalt-catalyzed cross-coupling reactions of alkyl halides with aryl Grignard reagents and their application to sequential radical cyclization/cross-coupling reactions

Reactions of alkyl halides with arylmagnesium bromides in the presence of cobalt(II)(diphosphine) complexes are discussed. Treatment of 1-bromooctane with phenylmagnesium bromide with the aid of a catalytic amount of CoCl₂(dppp) [DPPP=1,3-bis(diphenylphosphino)propane] yielded octylbenzene in good yield. The reaction mechanism would include single electron transfer from an electron-rich cobalt complex to alkyl halide to generate the corresponding alkyl radical. The mechanism was justified by CoCl₂(dppe)-catalyzed [DPPE=1,2-bis(diphenylphosphino)ethane] sequential radical cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives that yielded benzyl-substituted cyclopentane skeletons.     

Features of two- and multicomponent heterocyclization reactions involving 3,4-disubstituted 5-aminopyrazoles and alkyl pyruvates

Three-component heterocyclizations of pyruvic acids and their esters with 5-aminopyrazoles and aromatic aldehydes, in addition to the sequential versions of these reactions, under different activating conditions were studied. Under conventional heating, pyrazolopyrimidine derivatives containing a hydroxyl group in the 6-position were formed in both two- and three-component treatments. Whereas the application of an inert atmosphere did not influence the outcome of these reactions, the use of ultrasonic irradiation led to the formation of 7-hydroxy-tetrahydropyrazolopyrimidines in multi-component reactions and 6-hydroxy-dihydropyrazolopyrimidines in the case of a step-by-step approach. The products of the latter treatment were further transformed into heteroaromatized 6-hydroxy-pyrazolopyrimidines by conventional heating.     

Heterogeneous palladium multi-task catalyst for sequential Heck-reduction-cyclization (HRC) reactions: influence of the support

An evaluation study of various palladium supports led to the selection of charcoal as the most efficient system for the preparation of oxindoles by sequential Heck-reduction-cyclization (HRC) reactions. The in situ prepared Pd0/C was not recyclable for further cross-coupling reactions but remains still highly active for reduction processes. The sustainable chemistry described herein allows extremely simple experimental protocol under mild conditions, free of any base, ligand and additive.     

有机化学反应中间体的质谱分析

有机化学反应中活性中间体的性质各异,对反应中间体的表征和研究对于阐明和确证反应机理、优化反应条件、筛选催化剂和发现新类型反应至关重要.近年来,质谱技术和在线微量采样技术的发展,极大程度地拓展了质谱学在该领域的应用.本文总结了近年来本领域发展的新策略、技术和方法,以及有机质谱技术在反应中间体研究中的应用.     

Recent advances in ionic liquids: green unconventional solvents of this century: part II

Abstract

In the second part of our paper, further recent developments of ionic liquids in selected name reactions of carbonyl chemistry such as Mannich, Reformatsky, Cannizaro, Streacker, Barbier, Pechmann, etc. are described.     

固态有机反应新进展

总结了一些典型的固态有机反应。由于固态反应的特性，多数固态有机反应表现出较溶液中更高的反应效率和更好的选择性，在某些情况下，利用光活性主体与反应物形成包结物，可实现对映选择性的不对称固态合成。     

The Enzymology of Organic Transformations: A Survey of Name Reactions in Biological Systems

Chemical reactions that are named in honor of their true, or at least perceived, discoverers are known as “name reactions”. This Review is a collection of biological representatives of named chemical reactions. Emphasis is placed on reaction types and catalytic mechanisms that showcase both the chemical diversity in natural product biosynthesis as well as the parallels with synthetic organic chemistry. An attempt has been made, whenever possible, to describe the enzymatic mechanisms of catalysis within the context of their synthetic counterparts and to discuss the mechanistic hypotheses for those reactions that are currently active areas of investigation. This Review has been categorized by reaction type, for example condensation, nucleophilic addition, reduction and oxidation, substitution, carboxylation, radical‐mediated, and rearrangements, which are subdivided by name reactions.     

Cobalt-catalyzed sequential cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives with Grignard reagents and their application to the synthesis of 1,3-diols

Cobalt/N-heterocyclic carbene system or cobalt/diamine combination effectively catalyzes sequential cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives with trialkylsilylmethyl, 1-alkynyl, and aryl Grignard reagents. The sequential cyclization/cross-coupling reactions are applied to the synthesis of 1,3-diols starting from siloxy-tethered 6-halo-1-hexene derivatives.     

Densely functionalized 1,2-dihydrobenzo[b][1,6]naphthyridines: one-pot synthesis via sequential Ugi and Heck reactions

A facile one-pot synthesis of functionalized 1,2-dihydrobenzo[b][1,6]naphthyridines is described via sequential Ugi four components using 2-chloroquinoline-3-carboxaldehydes, allyl amine, acetic acid, isocyanides and ligand free Heck reactions in good yields.     

A study of chemical reactions in coarse-grained simulations

We introduce a reaction model for use in coarse-grained simulations to study the chemical reactions in polymer systems at mesoscopic level. In this model, we employ an idea of reaction probability in control of the whole process of chemical reactions. This model has been successfully applied to the studies of surface initiated polymerization process and the network structure formation of typical epoxy resin systems. It can be further modified to study different kinds of chemical reactions at mesoscopic scale.     

Comparison of photomacrocyclization reactions of trimethylsilyl- and tributylstannyl-terminated phthalimido- and maleimido-polyethers

SET-promoted photomacrocyclization reactions of trimethylsilyl- and tributylstannyl-terminated phthalimido- and maleimido-polyethers were investigated. The results indicate that the excited state cyclization processes, which take place via sequential SET-destannation pathways, produce macrocyclic polyethers more efficiently than those involving sequential SET-desilylation routes do. In addition, differences in product distributions obtained from photoreactions of trimethylsilyl- and tributylstannyl-terminated maleimido-polylethers suggest that more than one mechanistic pathway is followed in excited-state reactions of the tin-containing substrates.     

Beta-lactam-forming photochemical reactions of N-trimethylsilylmethyl- and N-tributylstannylmethyl-substituted alpha-ketoamides

Two mechanisms have been proposed for the beta-lactam-forming photochemical reactions of alpha-ketoamides. One, suggested by Aoyama, involves excited-state H-atom abstraction while the other, put forth by Whitten, follows a sequential SET-proton-transfer route. The photochemical properties of N-trimethylsilylmethyl- and N-tributylstannylmethyl-substituted alpha-ketoamides were explored in order to gain information about the mechanism of this process and to develop a regioselective method for beta-lactam formation. The results of this effort show that (1) photoreactions of N-trimethylsilylmethyl-substituted alpha-ketoamides proceed by competitive H-atom abstraction and sequential SET-desilylation pathways and (2) a sequential SET-destannylation pathway is preferentially followed in photochemical reactions of the tributylstannylmethyl-substituted alpha-ketoamides.     

Amplification reactions in microanalysis. A survey

Amplification reactions have been known for a long time, even if not always under this name. They are an alternative to analyze very small amounts of substance. Definitions and basic terms are given and the various possibilities for such reactions so far known are discussed, not all of the methods described here are of practical use.     

Bifurcations on potential energy surfaces of organic reactions

A single transition state may lead to multiple intermediates or products if there is a post-transition-state reaction pathway bifurcation. These bifurcations arise when there are sequential transition states with no intervening energy minimum. For such systems, the shape of the potential energy surface and dynamic effects, rather than transition-state energetics, control selectivity. This Minireview covers recent investigations of organic reactions exhibiting reaction pathway bifurcations. Such phenomena are surprisingly general and affect experimental observables such as kinetic isotope effects and product distributions.     

Sequential one-pot combination of multi-component and multi-catalysis cascade reactions: an emerging technology in organic synthesis

Creating sequential one-pot combinations of multi-component reactions (MCRs) and multi-catalysis cascade (MCC) reactions is a challenging task that has already emerged as a new technology in synthetic organic chemistry. Through one-pot sequential combination of MCRs/MCC reactions, the chemical products (fine chemicals, agrochemicals and pharmaceuticals) that add value to our lives can be produced with less waste and greater economic benefits. Within this Emerging Area, we describe our recent developments and designs for sequential one-pot MCRs/MCC reactions to facilitate their realization as biomimetics in organic chemistry.     

An efficient regioselective synthesis of functionalized biphenyls via sequential reactions of aromatic aldehydes and β-keto esters or ketones

Knoevenagel/Michael/Aldol reactions of aromatic aldehydes and β-keto esters/ketones in a sequential manner yielded intermediate cyclohexanones in good yields. The latter, on oxidative aromatization with iodine, afforded functionalized biphenyls with at least one phenolic hydroxyl in moderate to good yields.     

Synthetic studies of GKK1032s: the asymmetric synthesis of the decahydrofluorene skeleton via a novel cyclization of silyl enol ether and sequential retro Diels-Alder and intramolecular Diels-Alder reactions

GKK1032s, which were isolated from the culture broth of Penicillium sp. GKK1032, exhibit antitumor activity. We constructed the fully elaborated decahydrofluorene skeleton of GKK1032s. The C-ring was constructed by intramolecular cyclization reaction between a chiral epoxide and silyl enol ether, and the dienophile moiety was introduced concurrently. In addition, the AB-rings were stereoselectively constructed using novel sequential retro Diels-Alder (DA) and intramolecular Diels-Alder (IMDA) reactions. Several further modifications of the IMDA adduct were carried out, leading to the asymmetric synthesis of the desired hydroxyester including nine stereo centers.