Search

Nucleophilic phosphine-catalyzed annulations are recognized as practical and powerful tools for synthesizing various cyclic compounds. Phosphine acceptors play a key role in nucleophilic phosphine catalysis. The design and synthesis of new phosphine acceptors that are able to introduce new zwitterionic intermediates with new reactivities into phosphine-catalyzed annulations is highly desirable. We recently applied proton-shift principles in the design of new phosphine acceptors, and we synthesized several new acceptors. With the use of these acceptors, we have developed several novel phosphine-catalyzed annulation reactions. In this account, we present a brief introduction to the design and application of a series of acidic-hydrogen-tethered electron-deficient acceptors for phosphine-catalyzed annulation reactions, categorized according to the type of atom (N–H, O–H, C–H) to which the acidic hydrogen is bound. 1 Introduction 2 Phosphine Acceptors Tethered with an Acidic N–H Group 3 Phosphine Acceptors Tethered with an Acidic O–H Group 4 Phosphine Acceptors Tethered with an Acidic C–H Group 5 Conclusions [ABSTRACT FROM AUTHOR]

A convergent, microwave-assisted protocol for the synthesis of disubstituted NH -imidazoles via nucleophilic catalysis is described. The substituted imidazoles are accessed via the intramolecular addition of a variety of amidoxime substrates to activated alkynes followed by a thermally induced rearrangement of the in situ generated O -vinylamid-oxime species. The unprotected imidazoles contain an aryl group at the 2-position as well as an ester moiety at the 4-position. [ABSTRACT FROM AUTHOR]

Asymmetric allylic amination of Morita–Baylis–Hillman (MBH) adducts with simple aromatic amines is successfully realized by nucleophilic amine catalysis. A range of substituted α-methylene-β-arylamino esters is accessed in moderate to high yields (up to 88%) and with excellent enantioselectivities (up to 97% ee). Inorganic fluorides are found to be able to improve the enantioselectivity of the allylic amination reaction. A pyrrole-2-carboxylate and a cyclic imide are also compatible with this catalytic system. A chiral 2,3-dihydroquinolin-4-one derivative is easily obtained from the allylic amination product. [ABSTRACT FROM AUTHOR]

1-Substituted allenylsilanes reacted with 3-alkoxycyclobutanones in the presence of TiCl4 to afford 8-oxabicyclo[3.2.1]octan-3- ones stereoselectively. Nucleophilic attack of allenylsilanes to a 1,4- zwitterionic intermediate formed from 3-alkoxycyclobutanones and TiCl4 followed by 1,2-silyl migration, five-membered cyclization with an alkoxy group, and seven-membered cyclization of titanium enolate was proposed. Deuteration and one-pot Peterson olefination suggested that alkyl titanium species were formed after cyclization to 8-oxabicyclo[ 3.2.1]octane skeletons. [ABSTRACT FROM AUTHOR]

A triphenylphosphine-promoted [3+2] cycloaddition of α,γ-bis-substituted allenoates and N-tosylaldimines followed by alkene isomerization was disclosed, affording a series of functionalized 2-pyrroline derivatives in moderate chemical yields with random diastereoselectivities. [ABSTRACT FROM AUTHOR]

A convenient, post-transformational reaction has been developed for the construction of highly diversified quinoline-fused triazolo-diazepinones featuring four diversification points by employing a catalyst-free Ugi four-component-nucleophilic substitution-intramolecular click cycloaddition sequence. This approach provides a wide scope of products with good yields and high bond-forming efficiency. [ABSTRACT FROM AUTHOR]

An intermolecular, quaternary carbon center forming [4+3] cycloaddition reaction catalyzed by Lewis base and Brønsted base has been successfully developed. The dual catalysis exhibits a superior ability to enable a previously challenging reaction, and the corresponding quaternary aza-spirocycloheptane oxindole scaffolds are efficiently synthesized with moderate to high yields. [ABSTRACT FROM AUTHOR]

A linear polystyrene functionalized with both nucleophilic DMAP groups and sterically hindered tertiary amine groups was synthesized and used homogeneously in a range of esterification reactions between alcohols and various carboxylic acid derivatives. The polymer was highly effective in such reactions where the DMAP groups served as catalytic groups. The ester products of these reactions could be isolated in high purity and yield without the need for chromatographic purification, and the polymer could be recovered and reused numerous times with no apparent decrease in utility. [ABSTRACT FROM AUTHOR]

A new method for the preparation of optically active α-methylidene-γ-lactones is presented. The developed strategy utilizes an intramolecular Rauhut-Currier reaction for a facile construction of the α-methylidene-γ-lactone framework. The reaction is catalyzed by a chiral phosphine and employs the principles of nucleophilic catalysis. It benefits from operational simplicity and uses readily available starting materials. [ABSTRACT FROM AUTHOR]

The article discusses a study concerning a method developed by the group of Professor Motomu Kanai at the University of Tokyo in Japan for generating carboxylic acid derived enolates under mild conditions for Mannich-type reactions. It highlights the two key aspects involved in the boron catalysis, the chemoselectivity and enantioselectivity. The significance of developing a method for structural modification and homologation of carboxylic acid derivatives is noted.

An economic and practical transformation from secondary alkyl-substituted propargyl acetates to a variety of nucleophilic substitution products was described. This reaction was catalyzed by inexpensive InCl3. High yields and excellent chemoselectivity were obtained. The five-, six-, and seven-membered propargyl cyclo�ethers were also successfully constructed by this protocol. [ABSTRACT FROM AUTHOR]

This Account chronicles our efforts in the development of the catalytic asymmetric Stetter reaction using chiral triazolium salts as small molecule organic catalysts. Advances in the mechanistically related azolium-catalyzed asymmetric benzoin reaction are discussed, particularly as they apply to catalyst design. A chronological treatise of reaction discovery, catalyst optimization and reactivity extension follows. 1 Introduction 2 Proposed Mechanism of the Benzoin and Stetter Reactions 3 The Benzoin Reaction 4 Synthesis of Chiral Bicyclic Triazolium Salts 4.1 Aminoindanol-Derived Bicyclic Scaffold 4.2 Phenylalanine-Derived Bicyclic Scaffold 5 The Intermolecular Stetter Reaction 6 The Asymmetric Intramolecular Stetter Reaction 6.1 Recent Contributions to the Asymmetric Intramolecular Stetter Reaction 6.2 Comparison of the Asymmetric Intramolecular Stetter �Reaction with Two Different Triazolium Carbene Scaffolds 6.3 Scope of the Intramolecular Stetter Reaction with Different Tethers 6.4 Electronic Effects of the Aromatic Backbone of the Aldehyde on the Intramolecular Stetter Reaction 6.5 Effects of the Michael Acceptor on the Asymmetric Intra-molecular Stetter Reaction 6.6 The Asymmetric Intramolecular Stetter Reaction of Aliphatic Aldehydes 7 Effects of Pre-existing Stereocenters on the Intramolecular Stetter Reaction 8 Synthesis of Quaternary Stereocenters via the Asymmetric Intramolecular Stetter Reaction 9 Synthesis of Contiguous Stereocenters via the Asymmetric Intramolecular Stetter Reaction 10 Asymmetric Synthesis of Hydrobenzofuranones via the Intramolecular Stetter Reaction 11 Applications to Total Synthesis 12 Summary and Outlook [ABSTRACT FROM AUTHOR]

Pyrrols are substructures in various biological active molecules. A straight forward iron-catalyzed synthesis of pyrrols via insertion of an imine into a vinylcyclopropane is presented. The corresponding pyrrols are obtained in moderate to good yields. Scope and limitations will be discussed. [ABSTRACT FROM AUTHOR]

The article discusses the synthesis and different usage of trimethylsilyl cyanide (TMSCN), a commercial reagent used as cyanide source for nucleophilic reactions. A description of the agent is offered. It states that TMSCN is generally used in nucleophilic additions to aldehydes, ketones and imines to form cyanohydrin silyl ethers2 and α-aminonitriles3 in Strecker-type reactions.