Au(I)-Catalyzed Oxidative Functionalization of Yndiamides.

Yndiamides, underexplored cousins of ynamides, offer rich synthetic potential as doubly nitrogenated two carbon building blocks. Here we report a gold-catalyzed oxidative functionalization of yndiamides to access unnatural amino acid derivatives, using a wide range of nucleophiles as a source of the amino acid side chain. The transformation proceeds under mild conditions, is highly functional group tolerant, and displays excellent regioselectivity through subtle steric differentiation of the yndiamide nitrogen atom substituents.

Convergent Total Syntheses of (-)-Rubriflordilactone†B and (-)-pseudo-Rubriflordilactone†B.

A highly convergent strategy for the synthesis of the natural product (-)-rubriflordilactone B, and the proposed structure of (-)-pseudo-rubriflordilactone B, is described. Late stage coupling of diynes containing the respective natural product FG rings with a common AB ring aldehyde precedes rhodium-catalyzed [2+2+2] alkyne cyclotrimerization to form the natural product skeleton, with the syntheses completed in just one further operation. This work resolves the uncertainty surrounding the identity of pseudo-rubriflordilactone B and provides a robust platform for further synthetic and biological investigations.

A General Copper-Catalyzed Synthesis of Ynamides from 1,2-Dichloroenamides.

Ynamides are accessed via copper-catalyzed coupling of Grignard or organozinc nucleophiles with chloroynamides, formed in situ from 1,2-dichloroenamides. The reaction exhibits a broad substrate scope, is readily scaled, and overcomes typical limitations in ynamide synthesis such as the use of ureas, carbamates, and bulky or aromatic amide derivatives. This modular approach contrasts with previous routes by installing both the N- and C-substituents of the ynamide as nucleophilic components.

Synthesis of Enantioenriched α-Chiral Bicyclo[1.1.1]pentanes.

Bicyclo[1.1.1]pentanes (BCPs), useful surrogates for para-substituted arenes, alkynes, and tert-butyl groups in medicinal chemistry, are challenging to prepare when featuring stereogenic centers adjacent to the BCP. We report the development of an efficient route to α-chiral BCPs, via highly diastereoselective asymmetric enolate functionalization. We also describe the application of this chemistry to the synthesis of BCP analogues of phenylglycine and tarenflurbil, the single enantiomer of the NSAID flurbiprofen.

Synthesis and applications of highly functionalized 1-halo-3-substituted bicyclo[1.1.1]pentanes.

Bicyclo[1.1.1]pentanes (BCPs) are important bioisosteres of 1,4-disubstituted arenes, tert-butyl and acetylenic groups that can impart physicochemical benefits on drug candidates. Here we describe the synthesis of BCPs bearing carbon and halogen substituents under exceptionally mild reaction conditions, via triethylborane-initiated atom-transfer radical addition ring-opening of tricyclo[1.1.1.01,3]pentane (TCP) with alkyl halides. This chemistry displays broad substrate scope and functional group tolerance, enabling application to BCP analogues of biologically-relevant targets such as peptides, nucleosides, and pharmaceuticals. The BCP halide products can be converted to the parent phenyl/tert-butyl surrogates through triethylborane-promoted dehalogenation, or to other derivatives including carbonyls, alcohols, and heterocycles.

Copper-Catalyzed Synthesis and Applications of Yndiamides.

The first synthetic route to yndiamides, a novel class of double aza-substituted alkyne, has been established by the copper(I)-catalyzed cross-coupling of 1,1-dibromoenamides with nitrogen nucleophiles. The utility of these compounds is demonstrated in a range of transition-metal-catalyzed and acid-catalyzed transformations to afford a wide variety of 1,2-diamide functionalized products.

A robust and modular synthesis of ynamides.

A flexible, modular ynamide synthesis is reported that uses trichloroethene as an inexpensive two carbon synthon. A wide range of amides and electrophiles can be converted to the corresponding ynamides, importantly including acyclic carbamates, hindered amides, and aryl amides. This method thus overcomes many of the limitations of other approaches to this useful functionality.