Catalyst economy. Part 2: Sequential metathesis—Kharasch sequences using the Grubbs metathesis catalysts

Sequential ring-closing metathesis (RCM)-Kharasch cyclizations are promoted by the Grubbs metathesis catalysts and provide rapid access to bicyclic lactones and lactams.     

Grubbs-inspired metathesis in the Moore group

Alkene metathesis has proven to be a powerful method for carbon carbon bond formation, particularly in the field of polymer and materials science. The availability of various tailor-made catalysts not only enables the synthesis of well-defined polymers but facilitates the development of functional, stimuli–responsive materials. This highlight, dedicated to Professor Robert Grubbs on his 75th birthday, focuses on the various research efforts in our group utilizing both alkene and alkyne metatheses and the interesting materials derived from them. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2935–2948     

Enolesters as chain end-functionalizing agents for the living ring opening metathesis polymerization

Functional enolethers have previously been used to introduce functional end groups at the chain end of ruthenium carbene complex initiated living ring opening metathesis polymers. Here, we investigated whether the weaker π-donating enolesters could equally be used in regio selective reactions with ruthenium carbene complexes and thus as polymer end-functionalization reagents. Enolesters such as vinyl acetate, butenyl acetate, 3-(4-(tert-butoxy)phenyl)propenyl acetate and 6-(((benzyloxy)carbonyl)amino)hex-1-en-1-yl acetate were used as living ROMP terminating agents. All gave the expected end groups proving that enolesters are synthetically easily accessible targets for living ROMP end-functionalization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2983–2990     

Toward the synthesis of amphidinolide P: optimization of a model ene–yne metathesis fragment coupling

Ene–yne cross metathesis was assessed for use as a key fragment coupling in a planned total synthesis of amphidinolide P. A terminal alkyne containing a β,γ-epoxide was synthesized and employed as the alkyne partner in an intermolecular ene–yne metathesis. In the alkene substrate, optimal functionality and reaction conditions were determined. An unprotected allyl alcohol was found to be critical for both high yield and high E-selectivity. Fewer equivalents of the alkene resulted in incomplete reaction and side reactions consumed the terminal alkyne. The best ruthenium carbene precatalysts were found to be the Hoveyda–Grubbs carbene complexes.     

A Molecular modeling study of the changes of some steric properties of the precatalysts during the olefin metathesis reaction

The productive self‐metathesis of 1‐octene with a series of new phosphine ligated Grubbs‐type precatalysts was studied. The resulting structures were used to compare some steric properties of the new precatalysts with those of well‐known precatalysts. The possibility of α‐CC agnostic stabilization as well as the ability of the ligands to shield the metal was studied. A comparison of the obtained data, pointed to the unlikelihood that α‐CC agostic stabilization is a major contribution to the stabilization of the various metallacyclobutane rings. The similarity in the ability of the ligands to shield the metal also raised questions about the comparison of experimentally observed trends with those obtained theoretically. © 2014 Wiley Periodicals, Inc.     

Grubbs carbene complex-catalyzed cleavage of allyl vic-diols to aldehydes with a co-oxidant: application to the selective cleavage of huge marine molecules

An oxidative cleavage of allyl vic-diols to aldehydes catalyzed by a Grubbs carbene complex using a co-oxidant has been established for the first time, with good yields. The utility of this selective cleavage reaction was demonstrated through the use of two huge marine molecules, symbiodinolide and N-p-BrBz palytoxin.     

Synthesis of polynorbornene‐poly(tert‐butyl acrylate) nanoparticles with original morphologies by tandem ROMP and ATRP in microemulsion

Composite latex particles based on homopolymers and graft‐copolymers composed of polynorbornene (PNB) and poly(tert‐butyl acrylate) (PtBA) were synthesized in microemulsion conditions by simultaneous combination of two distinct methods of polymerization: Ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Only one commercial compound (first generation Grubbs catalyst) was used to initiate the ROMP of norbornene (NB) and activate the ATRP of tert‐butyl acrylate (tBA). Well‐defined nanoparticles with hydrodynamic diameters smaller than 50 nm were prepared with original morphologies depending on the monomer compositions, the type of combination (polymer blend or graft‐copolymer), and the conditions of microemulsion polymerizations. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Total Synthesis of (+)‐Cryptocaryalactone and of a Diastereoisomer of (+)‐Strictifolione via Ring‐Closing Metathesis (RCM) and Olefin Cross‐Metathesis (CM)

Ring‐closing metathesis (RCM) and olefin cross‐metathesis (CM) reactions were used as the key steps for the synthesis of (+)‐cryptocaryalactone ( 1 ) and the first synthesis of the diastereoisomer 3 of (+)‐strictifolione, starting from the commercially available L ‐malic acid (=(2S)‐2‐hydroxybutanedioic acid).     

一元线性回归试验数据的优化

运用统计学处理平行试验数据中可疑值的原理,建立了一元线性回归试验数据的优化方法。其中Grubbs法适用于精密度要求较低的试验,4d法则适用于精密度要求较高的试验和确定两变量的线性范围。     

Branched Polymers via ROMP of Termimers

Today's olefin metathesis catalysts show high reactivity, selectivity, and functional group tolerance and allow the design of new syntheses of precisely functionalized polymers. Here the synthesis of a new end‐capping reagent is investigated allowing the introduction of a highly reactive activated ester end‐group at the polymer chain end as well as its prefunctionalization to directly introduce functional moieties. The versatility of this new end‐capping reagent is demonstrated by utilizing it to synthesize a so‐called termimer (a monomer with termination capabilities). Copolymerization of a norbornene derivative with the termimer leads to hyperbranched ring‐opening metathesis polymerization polymers as proven by gel permeation chromatography and MALDI‐ToF‐(matrix‐assisted laser desorption/ionization time of flight) mass spectrometry.