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A general method, focusing upon olefin metathesis, was developed for the recovery of homogeneous olefin metathesis catalysts from crude reaction solutions. This method utilizes the supramolecular host–guest interaction between an azobenzene-modified N-heterocyclic carbene ligand and a silica-grafted β-cyclodextrin to remove homogeneous catalyst in a heterogeneous manner, allowing for the recovery of more than 97% of ruthenium in solution. The robust and simple nature of the guest molecule allows for the application of this method to a wide range of homogeneous catalysts. This study reports the synthesis and characterization of the said precatalyst and host compound as well as proof-of-concept recovery trials for a number of common substrates, with the residual ruthenium content of reaction mixtures evaluated by inductively coupled plasma mass spectrometry.

We report the synthesis of a highly-functional macromonomer, and subsequent crosslinkable poly(ethylene glycol) (PEG)-based bottlebrush polymers prepared via graft-through ring-opening metathesis polymerization (ROMP). This work makes two important additions to the repertoire of bottlebrush polymers: (1) the first example of a catechol-derived brush adhesive relying on an internal ketone for post-polymerization modification; and (2) the post-polymerization modification is utilized to greatly affect the mechanical properties of the bulk material through oxime functionalization and subsequent metal-free click chemistry beginning from the innocuous, and easily introduced, internal ketone. This form of oxime ligation was demonstrated with a series of oxyamines, with degrees of functionalization on the range of 18–100%, while introducing further functionality in the form of azide groups, which were rapidly converted to corresponding triazoles via metal-free click chemistry using the crosslinker (1R, 8S, 9S)-bicyclo[6.1.0]non-4-yn-9-ylmethyl (BCN) bisfunctionalized PEG (Mn = ∼6000 g mol−1). Under these conditions, the transformation from soluble polymer solution to soft hydrogel occurs within minutes. The polymer described herein stands testament to the ability of modularly-designed macromonomers to dictate the structure and properties of downstream materials in a predicable fashion.

A highly removable N-heterocyclic carbene ligand for a transition-metal catalyst in aqueous media via host–guest interactions has been developed. Water-soluble adamantyl tethered ethylene glycol in the ligand leads a hydrophobic inclusion into the cavity of β-cyclodextrin. Ruthenium (Ru) olefin metathesis catalyst with this ligand demonstrated excellent performance in various metathesis reactions in water as well as in CH2Cl2, and removal of residual Ru was performed via filtration utilizing a host–guest interaction and extraction.

Allylic boronates are versatile intermediates in organic synthesis. Herein, we present an ‘ate-mediated allylic substitution’ (AMAS) approach to allylic boronates. Bifunctional vinylboroate/ allylic acetate esters react with Grignard reagents to form tertiary ­allylic boronates via an AMAS reaction. We demonstrate that the method tolerates a wide range of substrates and Grignard reagents.

The synthesis of a fused N-heterocyclic carbene complex is accomplished using a flow-chemistry approach where a fused N-herterocyclic imidazolium chloride is passed through a packed bed of copper(I) oxide. The identity of the resulting complex is confirmed via crystal structure, and the reactivity is examined in the context of alkene hydroboration. We demonstrate that this novel complex can perform the desired reaction whereas the carbene ­ligand alone cannot.

The catalytic regioselective hydroboration of propargylic alcohols and ethers was investigated using NHC-CuCl. We observe that different NHC-CuCl complexes catalyze hydroborations of propargylic substrates with opposite regioselectivity. A 6-NHC-CuCl complex provides α-selectivity whereas β-selectivity is achieved using a 5-NHC-CuCl complex. The reaction tolerates a wide range of functional groups.

We present a 6-NHC-Cu(I) complex that provides α-substituted allylboronates using allylic aryl ether substrates. The method was discovered by comparison of the chemoselectivities exhibited by complexes 1a, 1b, 2, and 3. We observed that 1a preferentially reacts with electron-rich alkenes over electron-deficient alkenes. Development of an asymmetric method revealed that 1b reacts with both the E and Z isomers to provide the same absolute configuration without showing E-Z isomerization. This stereoconvergent reaction occurs with high yields (av 86%), high S(N)2' selectivity (99:1), and high ee (av 94%) and exhibits wide functional-group tolerance using pure E or Z isomer or E/Z alkene mixtures. The stereoconvergent feature enables the use of many different olefination strategies for substrate production, including cross-metathesis. Chiral allylboronates could be purified by silica gel chromatography and stored in the freezer without decomposition.

An ate-mediated allylic substitution (AMAS) of vinylboronates is utilized in the divergent syntheses of the sugars methyl axenoside and methyl 3-epi-axenoside. Other key steps of the synthesis involve the dihydroxylation of the resulting allylic alcohol and selective oxidation of the resultant diol. Benefits of this methodology are also discussed.

Allylic boronates are versatile intermediates in organic synthesis. Herein, we present an ‘ate-mediated allylic substitution’ (AMAS) approach to allylic boronates. Bifunctional vinylboroate/ allylic acetate esters react with Grignard reagents to form tertiary ­allylic boronates via an AMAS reaction. We demonstrate that the method tolerates a wide range of substrates and Grignard reagents.

The catalytic regioselective hydroboration of propargylic alcohols and ethers was investigated using NHC-CuCl. We observe that different NHC-CuCl complexes catalyze hydroborations of propargylic substrates with opposite regioselectivity. A 6-NHC-CuCl complex provides α-selectivity whereas β-selectivity is achieved using a 5-NHC-CuCl complex. The reaction tolerates a wide range of functional groups.

The six-membered N-heterocyclic carbene-copper complex IQC catalyzes the asymmetric borylation of both the (E)- and (Z)-isomer of an allylic m-nitrophenyl ether to give the α-substituted allylboronate with the same absolute configuration.