نتایج جستجو برای: cyclizations

تعداد نتایج: 570  

Journal: :Beilstein Journal of Organic Chemistry 2007
Asunción Barbero Francisco J Pulido M Carmen Sañudo

Addition of low order phenyldimethylsilylcyanocuprates to allenes followed by "in situ" reaction of the intermediate silylcuprate with electrophiles ("the silylcuprate strategy") provides new routes for the synthesis of functionalised allylsilanes, which undergo highly stereocontrolled silicon-assisted intramolecular cyclizations leading to three to seven membered ring-formation.

Journal: :Molecules 2005
Naim H Al-Said Khaled Q Shawakfeh Wasim N Abdullah

Aryl free-radicals generated at the C-7 position of ethyl indole-2-carboxylates bearing N-allyl and propargylic groups triggered intramolecular cyclizations to furnish a new class of Duocarmycin analogues, formal ethyl pyrrolo[3,2,1-ij]quinoline-2- carboxylate derivatives, through the less favorable 6-endo-trig cyclization mode.

Journal: :Molecules 2014
Michael Gurry Ingrid Allart-Simon Patrick McArdle Stéphane Gérard Janos Sapi Fawaz Aldabbagh

(E)-3-Ylideneoxindoles are prepared in methanol in reasonable to good yields, as adducts of photochemical 5-exo-trig of aryl radicals, in contrast to previously reported analogous radical cyclizations initiated by tris(trimethylsilyl)silane and azo-initiators that gave reduced oxindole adducts.

Journal: :Molecules 2009
Lemuel Pérez-Picaso Jaime Escalante Horacio F Olivo María Yolanda Rios

Aqueous in situ one-pot N-Boc-deprotection-cyclization of N alpha-Boc-dipeptidyl-tert-butyl and methyl esters under microwave irradiation afforded 2,5-diketopiperazines (DKPs) in excellent yields. This protocol is rapid, safe, environmentally friendly, and highly efficient, and showed that the tert-butoxy moiety is also an excellent leaving group for these cyclizations.

2011
Christine Beemelmanns Hans-Ulrich Reissig

Samarium diiodide (SmI2) smoothly promotes the cyclizations of suitably substituted carbonyl compounds with styrene subunits leading to benzannulated cyclooctenes. The intramolecular samarium ketyl addition to arene or hetarene moieties enables a new, efficient, and highly stereoselective entry to dearomatized products such as hexahydronaphthalenes, steroid-like tetraor pentacyclic compounds, o...

Journal: :Chemical communications 2002
Koichi Mikami Hirofumi Ohmura

A synthetic approach for tropane alkaloids on the basis of tandem (domino) ene-type reactions of acetone silyl enol ethers with iminium ions is shown to be triggered by intermolecular ene-type reactions followed by 6-(2,5) silatropic ene-type cyclizations.

Journal: :Chemical communications 2013
Adele Faulkner James S Scott John F Bower

We report efficient Pd-catalyzed cyclizations of oxime esters with 1,1-disubstituted alkenes as the basis of a general entry to α,α-disubstituted pyrrolidine derivatives. We also demonstrate that catalytic asymmetric variants of this chemistry are feasible by employing a suitable chiral ligand.

Journal: :Chemical communications 2011
Nathalie Pinto Pascal Retailleau Arnaud Voituriez Angela Marinetti

Phosphine catalyzed enantioselective [3+2] cyclizations on 4-substituted 2,6-diarylidenecyclohexanones and 2,4-diarylidene-bicyclo[3.1.0]hexan-3-ones take place with high diastereo- and enantioselectivity levels. The process affords spirocyclic compounds with excellent stereochemical control of up to five stereogenic centres.

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