Lewis acid promoted cycloaddition reactions of donor–acceptor (DA) cyclopropanes are one the well‐studied approaches for construction heterocyclic and carbocyclic frameworks. During our efforts to exploit this strategy synthesis functionalization carbohydrate‐derived systems, we discovered nitriles with DA cyclopropanes. This personal account details contributions development cycloaddition. The reaction discovery, methods development, application in total along related examples from others...

In situ IR spectroscopy and transmetalation experiments confirm a postulated catalytic cycle. The metalloenolate 1 describes the active intermediate in aldol reaction catalyzed by [CuF2{(S)-tol-binap}] (see scheme). (S)-tol-binap=(S)-(−)-2,2′-bis(di-p-tolylphosphanyl)-1,1′-binaphthyl.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPhotochemical Promotion of the Intramolecular Pauson−Khand Reaction. A New Experimental Protocol for Cobalt-Catalyzed [2 + 2 1] CycloadditionsBrian L. Pagenkopf and Tom LivinghouseView Author Information Department Chemistry Biochemistry Montana State University, Bozeman, 59717Cite this: J. Am. Chem. Soc. 1996, 118, 9, 2285–2286Publication Date (Web):March 6, 1996Publication History Received26 October 1995Published online6 March 1996Published...

The annulation reaction between various indoles and 2-alkoxycyclopropanoate esters is reported. Both high efficiency complete stereochemical control were observed in some cases with this process. A single stereocenter on the cyclopropane controls diastereoselective formation of up to four new stereocenters. different course was 3-substituted indole substrates, an intervening C-3 C-2-migration process arose that gives synthetically useful C-2 alkylation products.

The total synthesis of (±)-goniomitine has been accomplished in 17 linear steps with 5.2% overall yield starting from commercially available δ-valerolactam. A synthetic highlight includes the first application a formal [3 + 2] cycloaddition between highly functionalized nitrile and donor−acceptor cyclopropane to prepare an indole nucleus. use microwave reactor is shown greatly improve reaction times for two steps.

The formal [4+3] cycloaddition of 2-alkoxy-1,1-dicarboxylate activated donor−acceptor cyclobutanes with nitrones is disclosed. reaction forms structurally unique oxazepines in moderate to high yield a wide scope nitrones. In most cases either diastereomeric mixture or single diastereomer may be formed, depending on the conditions.

A new synthesis of 2-alkoxy-1,1-cyclobutane diesters and their first use in dipolar cycloadditions is reported. Both the formation donor−acceptor cyclobutanes subsequent annulation with situ formed imines are catalyzed by Yb(OTf)3. Cyclobutanes carbon donor groups give piperidines high trans stereoselectivity.

Tandem ring opening, elimination, and cycloaddition of donor–acceptor cyclopropanes were observed in Yb(OTf)3-catalyzed with nitrosoarenes. The reaction results formation tetrahydro-1,2-oxazine instead the normal cycloadduct isoxazolidine via situ nitrone formation. A similar cascade sequence was cis-diazines. Mechanistic studies on this unique transformation offer an entirely new approach for design cyclopropanes.

Donor-acceptor cyclopropanes activated with Me3SiOTf cleave to reactive intermediates that can be efficiently intercepted by nitriles in a formal [3 + 2] dipolar cycloaddition reaction. Aliphatic, aromatic, and alpha,beta-unsaturated are excellent reaction partners, giving synthetically useful 2H-3,4-dihydropyrrole products high yield.

Electrochemical tuning and structural modification of thiophene-substituted siloles led to silole chromophores with efficient stable electrochemiluminescence (ECL). By extending π conjugation thiophene units by constraining the applied potential range, radical cations favorable for ECL emission were generated (see graph an example).

A new method for the synthesis of 5-azaindole derivatives is reported. [3+2] dipolar cycloaddition between nitriles and a 3,4-cyclopropanopiperidine followed by SeO2 oxidation affords target compounds in moderate to excellent yields. The divergent nature cost effectiveness this makes it very suitable combinatorial applications pharmaceutical industry.

The cycloaddition between 2-alkoxy-1,1-cyclobutane diesters and aromatic, heteroaromatic, or aliphatic aldehydes under Yb(OTf)3 catalysis generates tetrahydropyrans in high yields with exclusive cis-stereochemistry.

Lewis acid activated donor-acceptor cyclopropanes react with aliphatic, aromatic, and alpha,beta-unsaturated nitriles in a novel cascade [3 + 2] dipolar cycloaddition, dehydration, tautomerization sequence to afford pyrroles moderate excellent overall yield. This cost-effective regiospecific method is ideally suited for the preparation of combinatorial libraries. [reaction: see text]

The unique structural and bonding characteristics of fluorine engender distinctive electronic properties to transition metal complexes. This type complex has only lately been appreciated in asymmetric catalysis (see figure).

An efficient method is presented for the synthesis of novel donor-acceptor silole chromophores through selective monohalogenation 2,5-dimetallosiloles followed by Negishi alkyne cross-coupling reactions. The electronic properties and crystal packing these new siloles can be controlled judicious combinations peripheral functional groups.

Two new series of 2,2'-bipyrroles and 2,2'-thienylpyrroles have been prepared by trimethylsilyl trifluoromethanesulfonate (TMSOTf)-mediated reaction donor−acceptor cyclopropanes with 2-cyanopyrroles 2-cyanothiophene, respectively. This method opens the door toward a wide variety unsymmetrical bipyrroles thienylpyrroles.

The synthesis of a second-generation cobalt catalyst for the formation trans-THF products via Mukaiyama aerobic oxidative cyclization is reported. Two procedures have been developed with new water-soluble that give superior yields and greatly simplify purification compared to previous catalysts.

The Yb(OTf)3 catalyzed [4+2] cycloaddition between donor-acceptor cyclobutanes and nitrosoarenes is disclosed. This method facilitates the synthesis of tetrahydro-1,2-oxazines in good to excellent yields as single diastereomers. Except for a few electron-deficient nitrosoarenes, regioselectivity was observed throughout these studies.

Abstract The formal [3+2] dipolar cycloaddition (or annulation) of donor‐acceptor cyclopropanoate esters with pyridines and 5‐nitroquinoline is reported. Electron‐deficient pyridine dipolarophiles (R=CN, CO 2 Et, COMe) participate in the annulation whereas electron rich species do not. product 2,3‐dihydroindolizines undergo rapid autooxidation, X‐ray structures for two aromatic products are

The first total synthesis of (−)-aplysiallene has been completed in 16 steps and features a key sequential Mukaiyama aerobic oxidative cyclization to prepare the fused bis-THF core. original stereochemical assignment revised as shown.

Abstract The total synthesis of (±)‐quebrachamine has been completed in 13 linear steps and 17.8 % overall yield. indole core was constructed via a formal [3+2] dipolar cycloaddition between functionalized nitrile donor‐acceptor cyclopropane, the synthetically challenging nine‐membered ring secured by an efficient chloroacetamide photocyclization.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Compared to terminal alkynes, (methylthio)alkynes are generally superior substrates for the thermally promoted, Co2(CO)8 catalyzed Pauson-Khand reaction of enynes and allenynes, providing enones in higher yields with enhanced diastereoselectivity. Improvements yield dependent upon use 2,2,2-trifluoroethanol as co-solvent an apparent preference endo selectivity (ethoxy)alkynes also disclosed.

A new class of bis(oxazoline) ligands are introduced that feature o-alkoxyaryl substituents and provide the highest enantioselectivities yet reported for copper-catalyzed asymmetric dienosilane aldol addition to pyruvate glyoxylate esters. Enantioselectivities up 98% ee (before recrystallization) isolated yields 91% were observed. Additionally, chloride counterions found be superior triflate this reaction.