Intramolecular 1,3-Dipolar Cycloaddition Reactions

The intramolecular 1,3-dipolar cycloaddition reaction of suitably functionalized 1,3-dipoles represents a general scheme for the synthesis of novel fused ring heterocycles. Such reactions of a number of 1,3-dipoles are summarized and the general outline and potential analogies for these reactions noted. While the immediate aim of this review is to survey and correlate published work, it is hoped that general and specific points in need of study will be revealed and will stimulate further work in this fertile field.     

Cycloaddition Reactions of Enamines

This review includes information for around two last decades on cycloaddition reactions of enamines with various agents in order to build carbo- and heterocycles. In addition, the review presents organo-catalytic reactions in which enamines are intermediate products generated in situ. This review covers the synthesis of four, five, six and eight-membered carbocyclic compounds, as well as heterocycles as pyrroles, pyridines, etc.     

铑催化环加成反应的研究进展

综述了近几年铑催化剂在环加成反应中的研究进展, 主要包括[2＋2], [2＋2＋1], [2＋2＋2], [3＋2], [3＋4]和[4＋2]环加成反应等, 讨论了铑催化下的环加成反应及其机理.     

Study on Unexpected Cycloaddition Reactions of Imines with THF

Thesynthesisofnitrogen-containingheterocylesthroughcycloadditionreactionofimineshasstimulatedmuchpreparativeandmechanisticwork'".Whenweattemptedtosynthesizeapolycycliccompound3byadditionreactionofimineland5-norbornene-2,3-dicarboxylicacid2,however,unexpectedtricycliccompounds4and6wereobtainedinsteadofthedesignedproduct3(Schemcl).Heretetrahydrofuran(THF)servedasthesourceofdihydrofiJranwhichunderwentcycloadditionwithlgiving4and6.Ananalogousreactionwasnotedpreviouslyinthislaboratory'(Scheme2).…     

Transition-Metal-Catalyzed Cycloaddition Reactions to Access Seven-Membered Rings

The efficient and selective synthesis of functionalized seven-membered rings remains an important pursuit within synthetic organic chemistry, as this motif appears in numerous drug-like molecules and natural products. Use of cycloaddition reactions remains an attractive approach for their construction within the perspective of atom and step economy. Additionally, the ability to combine multiple components in a single reaction has the potential to allow for efficient combinatorial strategies of diversity-oriented synthesis. The inherent entropic penalty associated with achieving these transformations has impressively been overcome with development of catalysis, whereby the reaction components can be pre-organized through activation by transition-metal-catalysis. The fine-tuning of metal/ligand combinations as well as reaction conditions allows for achieving chemo-, regio-, diastereo- and enantioselectivity in these transformations. Herein, we discuss recent advances in transition-metal-catalyzed construction of seven-membered rings via combination of 2–4 components mediated by a variety of metals. An emphasis is placed on the mechanistic aspects of these transformations to both illustrate the state of the science and to highlight the unique application of novel processes of transition-metals in these transformations.     

One-Pot Functionalization of Graphene with Porphyrin through Cycloaddition Reactions

Two types of graphene‐based hybrid materials, graphene‐TPP (TPP=tetraphenylporphyrin) and graphene‐PdTPP (PdTPP=palladium tetraphenylporphyrin), were prepared directly from pristine graphene through one‐pot cycloaddition reactions. The hybrid materials were characterized by thermogravimetric analysis (TGA), by TEM, by UV/Vis, FTIR, Raman, and luminescence spectroscopy, and by fluorescence/phosphorescence lifetime measurements. The presence of the covalent linkages between graphene and porphyrin was confirmed by FTIR and Raman spectroscopy and further supported by control experiments. The presence of TPP (or PdTPP) in the hybrid material was demonstrated by UV/Vis spectroscopy, with TGA results indicating that the graphene‐TPP and graphene‐PdTPP hybrid materials contained approximately 18 % TPP and 20 % PdTPP. The quenching of fluorescence (or phosphorescence) and reduced lifetimes suggest excited state energy/electron transfer between graphene and the covalently attached TPP (or PdTPP) molecules.     

Fluorescent Azasteroids through Ultrasound Assisted Cycloaddition Reactions

We report here the synthesis and optical spectral properties of several new azasteroid derivatives. The formation of these compounds was explained based on the most probable mechanism. The luminescent heterocycles were synthesized by 1,3-dipolar cycloaddition reactions between benzo[f]quinoline and methylpropiolate or dimethyl acetylenedicarboxylate (DMAD). A selective and efficient way for [3+2]-dipolar cycloaddition of benzo[f]quinolinium ylides under ultrasound (US) irradiation (20 kHz processing frequency) is presented. We report substantially higher yields under US irradiation, whereas the solvent amounts required are at least three-fold less compared to classical heating. The azasteroid derivatives are blue emitters with λ_max of fluorescence around 430–450 nm. A certain influence of the azasteroid substituents concerning absorption and fluorescent properties was observed. Compounds anchored with a bulky pivaloyl group or without a C=O carbonyl group have shown increased fluorescence intensity.     

Versatile Cycloaddition Reactions of 1-Alkyl-1,2-Diphospholes

Abstract

The reactivity of 1-alkyl-1,2-diphospholes in cycloaddition reactions with dienes, dienophiles or 1,3-dipoles was examined. 1-Alkyl-1,2-diphospholes (2 ) exhibit dual reactivity and act as diene toward maleic acid derivatives or as dienophiles with 2,3-dimethyl-1,3-butadiene. The 1-alkenyl-1,2-diphospholes (4 ) are readily involved in intramolecular [4 + 2] cycloaddition reactions leading to cage phosphines (5 ). Interaction of 1-alkyl-1,2-diphospholes (2) with 1,3-dipolar reagents (diphenyldiazomethane and nitrones) results in formation of the bicyclic phosphiranes (8) and dimers of 1-alkyl-1,2-diphosphole oxides (9) or bicyclic phosphine oxides (10) with a β-lactam moiety depending on temperature.     

Fluorinated Imines in Tandem and Cycloaddition Reactions

The chemistry of fluorinated compounds has experienced extraordinary growth in recent decades due to the many and varied properties which many of the compounds that contain fluorinated groups possess. Among all of them, fluorinated chiral imines, in particular the Ellman's imines, are of great importance since they are some of the most interesting building blocks for the synthesis of a large number of enantioenriched carbocycles and heterocycles with extraordinary biological and synthetic properties. This personal account covers the most significant results obtained in our research group in the last two decades concerning asymmetric tandem reactions, paying special attention to the intramolecular aza-Michael reaction (IMAMR), diversity oriented synthesis (DOS), asymmetric tandem reactions involving a p-tolylsulfinyl group as chiral inducer and cycloaddition processes, in particular, the Pauson-Khand reaction, [2+2+2]-cycloadditions and metathesis reactions, starting mainly from enyne compounds and through the use of fluorinated chiral N-sulfinyl imines and their derivatives as starting materials.     

固相载体上的环加成反应及其应用

固相有机合成和组合化学是近年来发展起来的快速合成数种有机化合物的新方法。本文介绍了在固相载体上进行的环加成反应, 及其在有机合成及反应机理研究中的应用。     

Highly Enantio- and Diastereoselective Catalytic Asymmetric Tamura Cycloaddition Reactions

The first broad-scope catalytic asymmetric Tamura cycloaddition reactions are reported. Under the influence of anion-binding bifunctional catalysis a wide range of α,β-unsaturated N-trityl imines undergo reactions with enolisable anhydrides to form highly synthetically useful α-tetralone structures with excellent enantio- and -diastereocontrol. In stark contrast to the previous literature benchmarks, doubly activated or highly electron deficient alkenes are not required. A facile two-step, high yielding sequence can convert the cycloadducts to α-haloketones (challenging to generate catalytically by other means) with the net formation of two new C−C bonds and three new contiguous stereocentres with exquisite stereocontrol. A DFT study has provided insight into the catalyst mode of action and the origins of the observed enantiocontrol.     

有机催化不对称[4+2]环加成反应

有机催化不对称合成反应是目前国内外研究最为活跃的领域之一。不对称[4+2]环加成（Diels-Alder）反应是合成光学活性环状化合物的有效手段,目前报道的催化不对称Diels-Alder反应的有机催化剂主要有手性咪唑啉酮、手性Br?nsted酸、手性伯胺、金鸡纳碱衍生物等。本文对各类有机催化剂在有机催化不对称Diels-Alder反应中的应用研究进展,以及不对称诱导反应的机理进行了评述。     

N‐Alkylsulfonylimines as Dipolarophiles in Cycloaddition Reactions

First described in the late 1960s, N‐alkylsulfonylimines are heterocumulenes that participate in reactions with a range of 1,3‐dipoles to afford interesting 3‐, 4‐, 5‐, and 6‐membered heterocycles. The distribution of adducts obtained suggests that multistage, stepwise mechanistic pathways rather than a concerted process are in operation.     

有机膦催化环化及环加成反应在天然产物全合成中的应用研究进展*

有机膦小分子催化是一种反应条件温和、环境友好的有机合成方法,已广泛应用于有机合成领域。其中亲核有机膦催化的环化及环加成反应已经逐渐发展成为构建碳环和杂环化合物以及天然产物的重要工具之一。通过介绍近年来发展的有机膦催化环化及环加成反应的方法学,综述了近年来有机膦催化的环化及环加成反应在天然产物全合成中的应用研究进展。     

Metal‐Free [2+2+2] Cycloaddition of Ynamides and Nitriles: Mild and Regioselective Synthesis of Fully Substituted Pyridines

A metal‐free trimolecular [2+2+2] cycloaddition of internal ynamides and nitriles for de novo synthesis of fully substituted pyridines is disclosed. With the versatile Brønsted acid catalyst HNTf₂, the mild intermolecular cyclotrimerization process proceeds with complementary chemoselectivity and excellent regioselectivity.