Over the past 40 years, intramolecular hydroacylation has favored five-membered rings, in preference to four membered rings. Herein, we report a catalyst derived from earth-abundant cobalt that enables preparation of cyclobutanones, with excellent regio-, diastereo-, and enantiocontrol, under mild conditions (2 mol % catalyst loading and as low as 50 °C).

Phosphonate-directed ortho C–H borylation of aromatic phosphonates is reported. Using simple starting materials and commercially accessible catalysts, this method provides steady access to o-phosphonate arylboronic esters bearing pendant functionality and flexible substitution patterns. These products serve as flexible precursors for a variety of highly substituted phosphoarenes, and in situ downstream functionalization of the products is described.

We report an asymmetric homocoupling of ortho-(iodo)­aryl­phosphine oxides and ortho-(iodo)­aryl­phosphonates resulting in highly enantio­enriched axially chiral bisphosphine oxides and bisphosphonates. These products are readily converted to enantio­enriched biaryl bisphosphines without need for chiral auxiliaries or optical resolution. This provides a practical route for the development of previously uninvestigated atropo­selective biaryl bisphosphine ligands. The conditions have also proven effective for asymmetric dimerization of other, non-phosphorus-containing aryl halides.

The preparation of tertiary nitroalkanes via the nickel-catalyzed alkylation of secondary nitroalkanes using aliphatic iodides is reported. Previously, catalytic access to this important class of nitroalkanes via alkylation has not been possible due to the inability of catalysts to overcome the steric demands of the products. However, we have now found that the use of a nickel catalyst in combination with a photoredox catalyst and light leads to much more active alkylation catalysts. These can now access tertiary nitroalkanes. The conditions are scalable as well as air and moisture tolerant. Importantly, reduction of the tertiary nitroalkane products allows rapid access to α-tertiary amines.

High-throughput experimentation (HTE) workflows are efficient means of surveying a broad array of chiral catalysts in the development of catalytic asymmetric reactions. However, the use of traditional high-pressure liquid chromatography (HPLC)-UV/vis methodology to determine enantiomeric excess (ee) from the resulting reactions is often hampered by coelution of other reaction components, resulting in erroneous ee determination when crude samples are used and ultimately requiring product isolation prior to ee analysis. In this study, using four published reactions selected as model systems, we demonstrate that the use of liquid chromatography–mass spectrometry (LC–MS), supercritical fluid chromatography–mass spectrometry (SFC-MS), and selected ion monitoring (SIM) mass chromatography provides a highly accurate means to determine the ee of products in crude reaction samples using commonplace, low-cost MS detectors. Using ion selection, coeluting signals can be deconvoluted to provide accurate integrations of the target analytes. We also show that this method is effective for samples lacking UV/vis chromophores, making it ideal for HTE workflows in asymmetric catalysis.

Using a commercially available, inexpensive, and abundant copper catalyst system, an efficient α-functionalization of nitroalkanes with propargyl bromides is now established. This mild and robust method is highly functional group tolerant and provides straightforward access to complex secondary and tertiary homopropargylic nitroalkanes. Moreover, the utility of these α-propargylated nitroalkanes is demonstrated through downstream functionalization to biologically relevant, five-membered N-heterocycles such as pyrroles and 2-pyrrolines.

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