Flow chemistry-enabled studies of rhodium-catalyzed hydroformylation reactions.

We present an automated microscale flow chemistry platform for rapid performance evaluation of continuous and discrete reaction parameters in homogeneous hydroformylation reactions. We demonstrate the versatility of the developed microfluidic platform through a systematic study of the effects of a library of phosphine-based ligands on catalytic activity and regioselectivity.

Tuning the Porphyrin Building Block in Self-Assembled Cages for Branched-Selective Hydroformylation of Propene.

Unprecedented regioselectivity to the branched aldehyde product in the hydroformylation of propene was attained on embedding a rhodium complex in supramolecular assembly L2, formed by coordination-driven self-assembly of tris(meta-pyridyl)phosphine and zinc(II) porpholactone. The design of cage L2 is based on the ligand-template approach, in which the ligand acts as a template for cage formation. Previously, first-generation cage L1, in which zinc(II) porphyrin units were utilized instead of porpholactones, was reported.

Grade 2 spondylolisthesis at L4-5 treated by XLIF: safety and midterm results in the "worst case scenario".

Unlabelled: Spondylolisthesis is one of the most common indications for spinal surgery. However, no one approach has been proven to be more effective in treating spondylolisthesis. Recent advances in minimally invasive spine technology have allowed for different approaches to be applied to this indication, notably extreme lateral interbody fusion (XLIF).

Economics of less invasive spinal surgery: an analysis of hospital cost differences between open and minimally invasive instrumented spinal fusion procedures during the perioperative period.

Background: There is great debate about the costs and benefits of technology-driven medical interventions such as instrumented lumbar fusion. With most analyses using charge data, the actual costs incurred by medical institutions performing these procedures are not well understood. The object of the current study was to examine the differences in hospital operating costs between open and minimally invasive spine surgery (MIS) during the perioperative period.

Clinical and radiographic outcomes of extreme lateral approach to interbody fusion with β-tricalcium phosphate and hydroxyapatite composite for lumbar degenerative conditions.

Background: Historically, iliac crest bone graft has been used as the graft of choice for lumbar spine fusion procedures. Because fusion techniques have become less invasive, the demand for minimally disruptive grafting options has increased. This prospective study was performed to assess clinical and radiographic outcomes of patients treated with an iliac crest bone graft alternative and lateral lumbar interbody fusion.

Lumbar fusion in octogenarians: the promise of minimally invasive surgery.

Study Design: Retrospective chart review of prospectively collected data from 2 nonrandomized, nonconcurrent cohorts.

Objective: Early results of 2 lumbar interbody fusion procedures-open posterior lumbar interbody fusion (PLIF) and minimally invasive (extreme lateral interbody fusion [XLIF])-were compared in octogenarians to demonstrate the safety of each in the extreme elderly populations.

Summary Of Background Data: Although spinal pathologies are common in the elderly patients, additional health conditions often preclude operative treatment because anesthesia, blood loss, and recovery are too demanding.

Role of the cocatalyst in the copolymerization of CO2 and cyclohexene oxide utilizing chromium salen complexes.

The mechanism of the copolymerization of cyclohexene oxide and carbon dioxide to afford poly(cyclohexylene)carbonate catalyzed by (salen)CrN3 (H2salen = N,N,'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylene-diimine) in the presence of a broad range of cocatalysts has been studied. We have previously established the rate of copolymer formation to be very sensitive to both the electron-donating ability of the salen ligand and the [cocatalyst], where N-heterocyclic amines, phosphines, and ionic salts were effective cocatalysts. Significant increases in the rate of copolymerization have been achieved with turnover frequencies of approximately 1200 h(-1), thereby making these catalyst systems some of the most active and robust thus far uncovered.

Cyclohexene oxide/CO2 copolymerization catalyzed by chromium(III) salen complexes and N-methylimidazole: effects of varying salen ligand substituents and relative cocatalyst loading.

A detailed mechanistic study into the copolymerization of CO2 and cyclohexene oxide utilizing CrIII(salen)X complexes and N-methylimidazole, where H2salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine and other salen derivatives and X = Cl or N3, has been conducted. By studying salen ligands with various groups on the diimine backbone, we have observed that bulky groups oriented perpendicular to the salen plane reduce the activity of the catalyst significantly, while such groups oriented parallel to the salen plane do not retard copolymer formation. This is not surprising in that the mechanism for asymmetric ring opening of epoxides was found to occur in a bimetallic fashion, whereas these perpendicularly oriented groups along with the tert-butyl groups on the phenolate rings produce considerable steric requirements for the two metal centers to communicate and thus initiate the copolymerization process.

(Salen)CrIIIX catalysts for the copolymerization of carbon dioxide and epoxides: role of the initiator and cocatalyst.

The copolymerization of CO(2) and cyclohexene or propylene oxide has been examined employing (salen)Cr(III)Nu complexes (Nu = Cl or N(3)) as catalysts. The addition of various cocatalysts, including phosphines and PPN+ or Bu4N+ Cl- salts serves to greatly enhance the rate of copolymer production. In these instances, the mechanism of the initiation step appears to be unimolecular in catalyst concentration, unlike the bimolecular process cocatalyzed by N-methylimidazole.

The copolymerization of carbon dioxide and [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane catalyzed by (salen)CrCl. Formation of a CO2 soluble polycarbonate.

The copolymerization of 2-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane and carbon dioxide catalyzed by (salen)Cr(III)Cl (H(2)salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine) with 2.5 equiv of N-MeIm as cocatalyst affords a polycarbonate devoid of polyether linkages, along with only a trace quantity of cyclic carbonate. The presence of the trimethoxysilane functionality in the epoxide not only provided the reactant monomer and product copolymer high solubility in liquid carbon dioxide but also provided the ability to cross-link the copolymer and thereby greatly alter the physical properties of the thus formed polycarbonate.

Carbon dioxide/epoxide coupling reactions utilizing Lewis base adducts of zinc halides as catalysts. Cyclic carbonate versus polycarbonate production.

The reactions of zinc halides with 2,6-di-methoxypyridine or 3-trifluoromethylpyridine in dichloromethane have led to the formation of quite different complexes. Specifically, reactions involving pyridine containing electron donating methoxy substitutents have provided salts of the type [Zn(2,6-dimethoxypyridine)4][Zn2X6], as revealed by elemental analysis and X-ray crystallography. On the other hand, simple bis-pyridine adducts of zinc halides were isolated from the reactions involving the pyridine ligand with electron withdrawing substituents and characterized by X-ray crystallography, for example, Zn(3-trifluoromethylpyridine)2Br2.