Intramolecular reaction

About: Intramolecular reaction is a research topic. Over the lifetime, 5015 publications have been published within this topic receiving 138213 citations.

Reaction of Enol Ethers with Alkynes Catalyzed by Transition Metals: 5exo-dig versus 6endo-dig Cyclizations via Cyclopropyl Platinum or Gold Carbene Complexes

Abstract: The intramolecular reaction of enol ethers with alkynes in methanol is catalyzed by electrophilic Pt I I , Pd I I , and Au I I I chlorides and by a Cu 1 complex to give five- or six-membered rings bearing dimethyl acetals. The reaction takes place by an anti addition of the enol ether and the metal to the alkyne. The possible involvement of vinylidene complexes in this reaction is excluded. In addition to the usual 5-exo-dig (or 6-exo-dig) pathways, a 6-endo-dig pathway has also been found to take place with certain enynes. One case of 5-endo-dig cyclization has also been found. A general scheme for the alkoxycyclization of enynes catalyzed by transition metals based on DFT calculation of PtCl 2 and AuCl 3 complexes that includes exo and endo cyclizations is presented.

Pd-catalyzed alkyl to aryl migration and cyclization: an efficient synthesis of fused polycycles via multiple C-H activation.

Abstract: A novel palladium migration methodology for the synthesis of complex fused polycycles has been developed. This process involves 1,4-palladium alkyl to aryl migrations via through-space C−H activation, followed by intramolecular arylation or an intermolecular Heck reaction providing a very efficient way to synthesize fused ring systems.

Organocatalytic Michael cycloisomerization of bis(enones): the intramolecular Rauhut-Currier reaction.

Abstract: The utilization of enones as latent enolates enables regioselective enolate formation from chemically robust presursors. In this communication, we report a catalytic Michael cycloisomerization of bis(enones) under Morita−Baylis−Hillman conditions. Upon exposure to 10 mol % tributylphosphine, bis(enone) substrates afford both five- and six-membered ring products. Notably, unsymmetrical bis(enones) possessing sufficient steric or electronic bias yield single isomeric products.

Palladium catalyzed synthesis of heterocycles

Abstract: Novel procedures of constructing heterocycles are described which employ palladium catalyzed intramolecular addition of amino or hydroxyl group to an acetylene bond as a key reaction. Pyrroles and furans are prepared from l-amino-3-alkyn-2-ols and 3-alkyne-l,2-diols, respectively. Successive addition of two hydroxyl groups to one acetylene bond gives various types of acetals. Insect pheromones containing intramolecular acetal linkage are produced by applying this reaction. INTRODUCTION Ilydration of unactivated acetylenes to form ketones has found considerable synthetic use (Ref. 1). Terminal acetylenes almost invariably yield methyl ketones. Regioselective hydration of internal acetylenes stems from anchimeric assistance (Ref. 2,3) and intramolecular reaction of hydroxyl group to acetylene bond plays a key role to synthesize prostacyclin (Ref. 3,4). The above described reactions are usually catalyzed by mercuric salts. Intramolecular addition of protic group such as amino and hydroxyl to carbon carbon triple bond seems to be promising to construct venous kinds of heterocycles. Studies on the subject utilizing palladium catalyst are described in this paper. INTRAMOLECULAR ADDITION OF HYDROXYL OR AMINO GROUP TO ACETYLENES Palladium(II) species have been found to be effective to the intramolecular addition of hydroxyl across acetylenes. Regioslelctivity of the reactions is illustrated by the cases of 3-, 4-, and 5-alkyn-l-ols. Reactions are carried out in anhydrous ether utilizing PdCl2(PhCN)., as catalyst (condition A) or in aqueous acetonitrile utilizing PdC12 as catalyst (condition B). Under condition A, 3-decyn-l-ol cyclizes in 5-Endo-Dig manner giving dihydrofuran 2 as a predominant product. Reaction under condition B gives exclusively hydroxy ketone 3 which is the hydrolyzed product of 2. CH3(CH2)5CECCH2CH2OH CH (CH ) 4[) + CH3(CH2)5(CH2)3OH 3 25 0 0 I A: PdC12(PhCN)2 (0.01—0.03 equiv.) 30% anhydrous Et2O, r.t., 5-10 h B: PdCl2 (0.01—0.05 equiv.) aqueous CH3CN, ref lux 30 mm. 5-Undecen-l-ol cyclizes in 6-Exo-Dig manner and gives dihydropyran 5 and its hydrolyzed hydroxy ketone 6.

Palladium-catalyzed intramolecular asymmetric hydroamination of alkynes.

Abstract: The Pd-catalyzed reaction of internal alkynes with tethered amino groups in the presence of PhCO2H and RENORPHOS as chiral phosphine ligand is reported. Various five- and six-membered nitrogen-containing heterocycles were obtained in good to high yield with moderate to high ee.