Triquinanes from linear ketones via trimethylenemethane diyls

Linear compounds containing a ketone and diene functional groups reacted with the anion of TMS-diazomethane to produce alkylidene carbenes that underwent intramolecular cyclopropanation followed by the formation of trimethylenemethane diyls which underwent [2+3] cycloaddition reaction to produce linearly fused triquinanes.     

Cycloaddition reactions of trimethylenemethane diyls generated from alkynyl iodonium salts

Intramolecular [2+3] cycloaddition reaction of trimethylenemethane diyls that were generated successfully from the reaction of malonate anions containing diene units with propynyl iodonium salts via alkylidene carbene intermediates produced linearly fused triquinanes.     

Triquinanes from linear alkylidene carbenes via trimethylenemethane diyls

The intramolecular [2+3] cycloaddition reaction of the trimethylenemethane diyl generated from the intramolecular cyclopropanation reaction of alkylidene carbene produced linearly fused triquinanes regio- and stereoselectively. The current tandem cycloaddition reaction was applied to a 14-step total synthesis of hirsutene from methallyl alcohol.     

Palladium-catalyzed asymmetric [3 + 2] trimethylenemethane cycloaddition reactions

Transition-metal-catalyzed trimethylenemethane (TMM) [3 + 2] cycloadditions provide direct routes to functionalized cyclopentanes. This reaction has been shown to be a highly chemo-, regio-, and diastereoselective process. We report a palladium-catalyzed asymmetric [3 + 2] trimethylenemethane (TMM) cycloaddition between 3-acetoxy-2-trimethylsilylmethyl-1-propene and various di- and trisubstituted olefins. Yields of exo-methylenecyclopentane products range from 59 to 99%, and enantiomeric excesses range from 58 to 92% ee.     

Addition and cycloaddition reactions of allenyl cations with various cycloalka-1,3-dienes

Allenyl cations

, generated $\text{in}$$\text{situ}$ from propargyl chlorides and zinc chloride give monocyclic adducts or [3+4] and [2+4] cycloaddition products with various cycloalka-1,3-dienes. The mode of addition depends on R and the ring size of the 1,3-dienes.     

Ruthenium-catalysed carbenoid cyclopropanation reactions with diazo compounds

The transition-metal catalysed cyclopropanation of olefinic bonds using diazo compounds as a carbene source is among the best developed and most useful transformations available to the synthetic organic chemist. Nevertheless, the quest for new catalyst/ligand systems continues in order to further extend the scope of this method and to identify more economical catalytic systems. In this tutorial review, several different ruthenium complexes are presented which have recently emerged as suitable catalysts for carbenoid cyclopropanation. For the model reaction--cyclopropanation of styrene(s) with diazoacetates--and also for some intramolecular cyclopropanation reactions highly remarkable results in terms of catalyst efficiency, product yields, dia- and enantioselectivity have been reported.     

Asymmetric polymerization via cycloaddition reactions

The reaction of N‐phthaloyl‐L ‐leucine acid chloride (1) with isoeugenol (2) was carried out in chloroform, and novel optically active isoeugenol ester derivative 3 as a chiral monomer was obtained in high yield. Compound 3 was characterized by ¹H‐NMR, IR, and mass and elemental analysis and then was used for the preparation of model compound 5 and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione, PhTD (4), was allowed to react with compound 3. The reaction is very fast and gives only one diastereomer of 5 via Diels–Alder and ene pathways in quantitative yield. In order to explain this diastereoselectivity, a nonconcerted two‐step mechanism involving benzylic cation (BC) and aziridinium (AI) have been proposed for the Diels–Alder and ene reactions, respectively. The polymerization reactions of novel monomer 3 with bis(triazolinedione)s [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (8) and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (9)] were performed in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and gave novel optically active polymers 10 and 11 via repetitive Diels–Alder–ene polyaddition reactions. These polymers have inherent viscosities in a range about 0.18–0.22 dL/g. Some physical properties and structural characterizations of these new polymers have been studied and are reported. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1211–1219, 1999     

Mechanism of the reactions of diazaphospholes with diazo compounds

Conclusions Diazaphospholes react with diazo compounds by the mechanism of 1,3-dipolar cycloaddition. The reaction of 2-acetyl-5-methyl-1,2,3-diazaphosphole with diphenyldiazomethane proceeds via the intermediate formation of the product of [2 + 3]-cycloaddition.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1376–1380, June, 1987.     

Catalytic [2+1] cycloaddition of diazo compounds to [60]fullerene

A catalytic method for the efficient synthesis of 5,6-open and 6,6-closed (2π+1π) fullerene adducts by [2+1] cycloaddition of ethyl 2-alkyl(hetaryl)-2-diazoacetates to [60]fullerene in the presence of a three-component catalyst Pd(acac)₂—PPh₃—Et₃Al have been developed.     

Novel porphyrin-quinone architectures via 1,3-dipolar cycloaddition reactions

Porphyrinic pyridinium ylides react with 1,4-benzoquinone and 1,4-naphthoquinone to afford novel meso-substituted indolizine porphyrins.     

Structure-reactivity problem in cycloaddition reactions to form heterocyclic compounds

The steric and electronic effects of substituents in both diene and dienophile components have been considered as the main factors that control the electronic character of (4+2)-cycloaddition leading to transitions between normal, neutral, and inverse Diels-Alder reactions.Institut für Organische Chemie der Universität Regensburg, Universitätsstr. 31, D-93040 Regensburg, Germany. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1307–1322, October, 1995. Original article submitted August 15, 1995.     

Regiospecific cycloaddition reactions using functionalized isoprenylsilane and related compounds

1-Alkoxy-3-trimethylsilylmethyl- and 1-alkoxy-3-trimethylsilyl-l,3-butadienes ($\text{1}$) were newly prepared. The cycloaddition reactions of $\text{1}$ with various dienophiles including heterodienophiles were found to proceed very smoothly in a perfectly regiospecific mode.     

Dipolar cycloaddition reactions of organic azides with some acetylenic compounds

Phenyl azide 1 and several substituted benzyl azides 2a-o underwent 1,3-dipolar cycloaddition reactions with dimethyl acetylenedicarboxylate 3, phenylacetylene 4 and ethyl propiolate 5 to afford the triazoles 6-13. The reactions of these azides with ethyl propiolate were found to be completely regiospecific.     

Catalytic cycloaddition of diazo amides to fullerene C60

An efficient catalytic method for cycloaddition of diazo amides to fullerene C₆₀ in the presence of the three-component catalyst Pd(acac)₂-PPh₃-Et₃Al was developed. The yields and selective formation of the target cycloadducts do not depend on the structure of the starting diazo compound.     

Progress in intermolecular and intramolecular reactions of thioamides with diazo compounds and azides

Reactions of thioamides with nitrogen-rich 1,3-dipoles, diazo compounds and azides, have been known for long time already. However in recent years introduction of catalysts of different types (rhodium-, ruthenium- and copper-containing and Lewis acids) as well as highly electrophilic sulfonyl azides, allowed the development of new methods for the synthesis of heterocycles, enamines and N-sulfonyl amidines. Moreover, a new methodology in organic synthesis, based on generation and subsequent transformations of α-diazocarbonyl compounds was created. Reactions of sulfonyl azides with thioamides undergo readily in mild conditions to produce different sorts of N-sulfonyl amidines and represent a new type of click-type processes. Most of the cited works were published in the current decade. Earlier seminal papers are also reviewed when they constitute the background for new synthetic methods which were developed further.     

Germanium-carbon versus germanium-nitrogen double-bond formation in the reactions between germylenes and diazo compounds

The reactions between methyl diazoacetate, HC(N₂)COOMe, and a range of germylenes L₂Ge [L = CH₃], NH₂, OCH₃, Ph, CH=CH₂, SiH₃, (H₃Si)₂N, and (H₃Si)₂CH] have been studied using MNDO calculations. Molecular and electronic structures have been determined for the transoid germaketimines L₂Ge=N-N=C(H)COOMe [the primary 11 adducts of L₂Ge and HC(N₂)COOMe], for their cyclic cisoid isomers, and for the germaethenes L₂Ge=C(H)COOMe. The intermediate L₂GeCH(N₂)COOMe was found to dissociate smoothly along the unique GeC bond when L = NH₂, OCH₃, or (H₃Si)₂N (so leading to no net reaction) but to undergo facile loss of N₂, forming the germaethene L₂Ge=C(H)COOMe, when L = CH₃, Ph, CH=CH₂, SiH₃, or (H₃Si)₂CH. The calculations thus enable the prediction of substantially different patterns of reactivity, and hence different products, in the reactions between diazo compounds and the two closely similar germylenes [(Me₃Si)₂N]₂Ge and [(Me₃Si)₂CH]₂Ge.     

Tricyclic-isoxazolidine analogues via intramolecular 1,3-dipolar cycloaddition reactions of nitrones

The tricyclic-isoxazolidine analogues tetrahydrothiochromenoisoxazoles, hexahydroisoxazolequinolines and tetrahydroisoxazolepyranopyridines were prepared by an intramolecular 1,3-dipolar cycloaddition reaction of a nitrone with an alkene. For N-alkylated hexahydroisoxazolequinolines, reduction of the reaction time from two days to 40 min was achieved using microwave heating. The cyclization to form tetrahydroisoxazolepyranopyridines only proceeded when the alkene was substituted with an electron withdrawing group.     

Palladium-catalyzed [3 + 3] cycloaddition of trimethylenemethane with azomethine imines

A palladium-catalyzed [3 + 3] cycloaddition of trimethylenemethane (TMM) with azomethine imines has been developed to produce hexahydropyridazine derivatives under simple and mild conditions. The use of substituted TMM precursors highlights the difference of this system from previously reported [3 + 2] cycloaddition of TMMs under palladium catalysis. The present [3 + 3] cycloaddition reactions are also applicable to couplings with nitrones.