Intramolecular reaction

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

Catalytic asymmetric intramolecular alpha-alkylation of aldehydes.

Abstract: The development of a general catalytic asymmetric aldehyde alpha-alkylation reaction constitutes a major challenge in organic synthesis. Here, we report the first and successful approach toward its solution: (S)-alpha-methyl proline catalyzes the intramolecular alkylation of various halo aldehydes to the corresponding formyl cyclopentanes, -cyclopropanes, or -pyrrolidines in excellent yields and enantioselectivities. Most remarkably, racemization, aldolization, or catalyst alkylation do not occur to any significant extend, further illustrating the power, mildness, and profound selectivity of enamine catalysis.

A Highly Enantio- and Diastereoselective Catalytic Intramolecular Stetter Reaction

Abstract: A highly enantio- and diastereoselective intramolecular Stetter reaction has been developed. Subjection of α,α-disubstituted Michael acceptors to an asymmetric intramolecular Stetter reaction results in a highly enantioselective conjugate addition and a diastereoselective proton transfer. Available evidence suggests the diastereoselective protonation occurs via intramolecular delivery to the sterically more hindered face of the enolate. The scope of the trisubstituted Michael acceptors has been examined and found to be broad with respect to the size of the α-substituent and nature of the Michael acceptor. Aliphatic and aromatic aldehydes were examined and found to afford the desired product in good overall yield with high enantio- and diastereoselectivity.

Room temperature hydroalkylation of electron-deficient olefins: sp3 C-H functionalization via a lewis acid-catalyzed intramolecular redox event.

Abstract: A practical method for the intramolecular hydroalkylation of electron-deficient olefins has been developed. The direct transformation of benzylic, tertiary, and sterically hindered secondary sp3 C-H bonds into C-C bonds under the action of a catalytic amount of a variety of Lewis acids is described. The mechanism of these transformations is proposed to involve a tandem hydride transfer/cyclization sequence.

New method for preparation of coumarins and quinolinones via Pd-catalyzed intramolecular hydroarylation of C-C triple bonds.

Abstract: A new and general method has been developed for preparation of coumarins and quinolinones by intramolecular hydroarylation of alkynes. Various aryl alkynoates and alkynanilides undergo fast intramolecular reaction at room temperature in the presence of a catalytic amount of Pd(OAc)(2) in a mixed solvent containing trifluoroacetic acid (TFA), affording coumarins and quinolinones in moderate to excellent yields with more than 1000 turnover numbers (TON) to Pd. The methodology proved to tolerate a number of functional groups such as Br and CHO. On the basis of isotope experiments, a possible mechanism involving ethynyl chelation-assisted electrophilic metalation of aromatic C-H bonds by in-situ generated cationic Pd(II) species has been discussed. Also the involvement of vinylcationic species has been suggested.