Trialkylborane-Mediated Propargylation of Aldehydes Using γ-Stannylated Propargyl Acetates

Synthesis of vinylidenecyclopropanes via gold(I)-catalyzed cyclopropanation of vinyl arenes with γ-stannylated propargyl esters

The reaction of γ-stannylated propargyl esters in the presence of a cationic gold(I) catalyst affords vinylidenecyclopropane derivatives as a mixture of diastereomers. The cis-geometry of the alkenes is almost entirely retained in the product. DFT calculations suggest the involvement of the gold(I)-stabilized propargyl cation as a resonance form of gold(I)-coordinated allenylidene species.

Metal-Free Wet Chemistry for the Fast Gram-Scale Synthesis of γ-Graphyne and its Derivatives

γ-Graphyne (GY), an emerging carbon allotrope, is envisioned to offer various alluring properties and broad applicability. While significant progress has been made in the synthesis of GY over recent decades, its widespread application hinges on developing efficient, scalable, and accessible synthetic methods for the production of GY and its derivatives. Here we report a facile metal-free nucleophilic crosslinking method using wet chemistry for fast gram-scale production of GY and its derivatives. This synthesis method involves the aromatic nucleophilic substitution reactions between fluoro-(hetero)arenes and alkynyl silanes in the presence of a catalytic amount of tetrabutylammonium fluoride, where the fluoride plays a crucial role in removing protective groups from alkynyl silanes and generating reactive alkynylides. Our comprehensive analysis of the as-prepared GY reveals a layered structure, characterized by the presence of the C(sp)-C(sp2) bond. The synthetic strategy shows remarkable tolerance to various functional groups and enables the preparation of diverse F-/N-rich GY derivatives, using electron-deficient fluoro-substituted (hetero)arenes as precursors. The feasibility of producing GY and derivatives from fluorinated (hetero)arenes through the metal-free, scalable, and cost-effective approach paves the way for broad applications of GY and may inspire the development of new carbon materials.

Highly Regioselective Propargylation/Allenylation of Organolanthanum Reagents with Aldehydes

The metal-mediated propargylation or allenylation of carbonyl compounds is well-adapted to the preparation of homopropargylic or allenylic alcohols, which are multifunctional intermediates in synthetic chemistry. However, the regioselectivity of reactions using propargyl or allenyl metal reagents is difficult to control, owing to the equilibrium between the two species. In our study, propargyl or allenyl organolanthanum reagents were prepared using trimethylsilylpropyne or prop-1-yn-1-ylbenzene substrates. The treatment of the organolanthanum reagents with aldehydes yielded the regioselective products, respectively. This study provides a better understanding of structural specificity and the special chemoselectivity of rare earth metal reagents.

Recent Advances in the Synthesis of Propargyl Derivatives, and Their Application as Synthetic Intermediates and Building Blocks

The propargyl group is a highly versatile moiety whose introduction into small-molecule building blocks opens up new synthetic pathways for further elaboration. The last decade has witnessed remarkable progress in both the synthesis of propargylation agents and their application in the synthesis and functionalization of more elaborate/complex building blocks and intermediates. The goal of this review is to highlight these exciting advances and to underscore their impact.

Diastereoselective Synthesis of Terminal Bromo-Substituted Propargylamines via Generation of Lithium Bromoacetylide and Addition to Chiral N-tert-Butanesulfinyl Aldimines

The stereoselective synthesis of terminal bromo-substituted propargylamines via in situ generation of lithium bromoacetylide from 1,2-dibromoethene and addition to Ellman chiral N-tert-butanesulfinyl aldimines is reported. Modest to good yields (43-85%) and diastereoselectivity (dr = 3:1 to >20:1) were achieved for a range of aryl, heteroaryl, alkyl, and α,β-unsaturated substrates. Terminal bromo-substituted propargylamines prepared via this method can be directly used in the frequently employed Cadiot-Chodkiewicz coupling to produce functionalized diynes. The method reported here increases the structural diversity of chiral terminal bromo-substituted propargylamines that can be readily synthesized as previous methods for the stereoselective synthesis of these compounds rely on amino acid precursors from the chiral pool.

Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

The propargylation of aldehydes promoted by microwave irradiation using allenylboron compounds in a chemo- and regioselective way is described. The corresponding products were obtained in short reaction time, high yield and purity without the need of any solvent when allenylboronic acid pinacol ester was used, or using a minimal amount of acetone when potassium allenyltrifluoroborate was used.