Recent developments in controlled C-H functionalization transformations continue to inspire new retrosynthetic disconnections. One tactic in C-H functionalization is the intermolecular C-H insertion reaction of rhodium-bound carbenes. These intermediates can undergo highly selective transformations through the modulation of the ligand framework of the rhodium catalyst. This work describes our continued efforts toward differentiating C-H bonds in the same molecule by judicious catalyst choice. Substituted cyclobutanes that exist as a mixture of interconverting conformers and possess neighboring C-H bonds within a highly strained framework are the targets herein for challenging the current suite of catalysts. Although most C-H functionalization tactics focus on generating 1,2-disubstituted cyclobutanes via substratecontrolled directing-group methods, the regiodivergent methods discussed in this paper provide access to chiral 1,1-disubstituted and cis-1,3-disubstituted cyclobutanes simply by changing the catalyst identity, thus permitting entry to novel chemical space.

Dirhodium triarylcyclopropanecarboxylate catalysts (Rh2TPCP4) are sterically demanding and capable of controlling the site selectivity of C–H functionalization by means of C–H insertion with donor/acceptor carbenes. This study compares the structures and reactivity profiles of dirhodium triarylcyclopropanecarboxylates with dirhodium diarylcyclopropanecarboxylates. The absence of the third aryl group makes the catalysts less sterically demanding and lacks a well-defined preferred conformation. The catalysts have a greater tendency for inducing C–H functionalization at tertiary C–H bonds versus their triaryl counterparts but are generally not capable of achieving high levels of asymmetric induction. These studies confirm the critical requirement of having at least three substituents on the cyclopropanecarboxylate ligands to have well-defined sterically demanding catalysts capable of high levels of asymmetric induction.

In the original Supplemental Information for this article, the NMR data for compound 8 on page S23 unfortunately contained data from a different but related compound that was ultimately not included in the paper. Additionally, supporting NMR spectra for compound 8 were inadvertently omitted from the section ''Nuclear Magnetic Resonance Spectra.'' Therefore, the NMR data have been corrected on page S23,

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