Effect of ligand backbone on the selectivity and stability of rhodium hydroformylation catalysts derived from phospholane-phosphites

We thank the Eastman Chemical Company for funding and permission to publish. M.B. thanks the School of Chemistry and EaStCHEM for support.A study on how ligand backbone structure has an impact on selectivity, rate, and catalyst stability of hydroformylation catalysts was prompted by some longer-term stability issues being discovered for a phospholane-phosphite with a [−CH2O−] backbone. A series of phospholane-phosphite ligands were synthesized. Catalysts made in situ from these ligands and [Rh(acac)(CO)2] were found to give iso-butanal selectivities up to 75% at temperatures between 75 and 105 °C: the latter being a benchmark for iso-selectivity in reactions conducted at industrially meaningful temperatures. A racemic rhodium complex of a bidentate phospholane-phosphite from a tropos-biphenol with an extended backbone showed unusually high stability at high temperatures, combined with even better iso-selectivity in propene hydroformylation relative to the original complex. A related ligand with an electron-withdrawing group maintained the unusually high stability and improved activity. Characterization of the precatalysts of type [RhH(CO)2(L)] was accomplished using in situ HPIR spectroscopy and backed up by density functional theory calculations (B3PW91-D3 level) and by NMR studies; the latter showed that the variation of the backbone also had a pronounced impact on the precatalyst structure. A key finding is that it is now possible to prepare phospholane-phosphite ligands that deliver high iso-butanal selectivity and that show no signs of degradation after several days even above typical reaction temperatures. In one stability test, several kilograms of aldehydes were produced with TOF and selectivity being consistent over several days.PostprintPeer reviewe

Risk factors for Coronavirus disease 2019 (Covid-19) death in a population cohort study from the Western Cape province, South Africa

Risk factors for coronavirus disease 2019 (COVID-19) death in sub-Saharan Africa and the effects of human immunodeficiency virus (HIV) and tuberculosis on COVID-19 outcomes are unknown. We conducted a population cohort study using linked data from adults attending public-sector health facilities in the Western Cape, South Africa. We used Cox proportional hazards models, adjusted for age, sex, location, and comorbidities, to examine the associations between HIV, tuberculosis, and COVID-19 death from 1 March to 9 June 2020 among (1) public-sector “active patients” (≥1 visit in the 3 years before March 2020); (2) laboratory-diagnosed COVID-19 cases; and (3) hospitalized COVID-19 cases. We calculated the standardized mortality ratio (SMR) for COVID-19, comparing adults living with and without HIV using modeled population estimates.Among 3 460 932 patients (16% living with HIV), 22 308 were diagnosed with COVID-19, of whom 625 died. COVID19 death was associated with male sex, increasing age, diabetes, hypertension, and chronic kidney disease. HIV was associated with COVID-19 mortality (adjusted hazard ratio [aHR], 2.14; 95% confidence interval [CI], 1.70–2.70), with similar risks across strata of viral loads and immunosuppression. Current and previous diagnoses of tuberculosis were associated with COVID-19 death (aHR, 2.70 [95% CI, 1.81–4.04] and 1.51 [95% CI, 1.18–1.93], respectively). The SMR for COVID-19 death associated with HIV was 2.39 (95% CI, 1.96–2.86); population attributable fraction 8.5% (95% CI, 6.1–11.1)

Grade 2 Spondylolisthesis at L4-5 Treated by XLIF: Safety and Midterm Results in the “Worst Case Scenario”

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). The risk, however, of using XLIF in treating grade II spondylolisthesis is the ventral position of the lumbar plexus, particularly at L4-5. Objective. This study reports the safety and midterm clinical and radiographic outcomes of patients with grade II lumbar spondylolisthesis treated with XLIF. Methods. 63 patients with grade II spondylolisthesis and spinal stenosis were treated with XLIF and were available for 12-month followup. Of those, 61 (97%) were treated at L4-5. Clinical (VAS, complications, and reoperation rate) and radiographic (anterolisthesis, disk height, and fusion) parameters were assessed. Study Design. Data were collected via a prospective registry and analyzed retrospectively. Results. Sixty-three patients were available for evaluations at least one year postoperatively. Average pain (visual analog scale) decreased from a score of 8.7 at baseline to 2.2 at 12 months postoperatively. Average anterior slippage was reduced by 73% and was well maintained. Average disk height (4.6 mm pre-op and 9.0 mm post-op) nearly doubled after surgery. Slight settling (average 1.3 mm) occurred over the twelve-month follow-up period. There were no neural injuries and no nonunions noted. Conclusions. XLIF is a safe and effective minimally invasive treatment alternative for grade II spondylolisthesis. Real-time neurological monitoring and attention to technique are mandatory

Suicide Attempts Among Transgender and Gender Non-Conforming Adults

New analysis of responses to the National Transgender Discrimination Survey (NTDS) shows that transgender respondents who experienced rejection by family and friends, discrimination, victimization, or violence have a higher risk of attempting suicide. 78 percent of survey respondents who suffered physical or sexual violence at school reported suicide attempts, as did 65 percent of respondents who experienced violence at work.The study suggests that several minority stressors – negative experiences related to anti-transgender bias – may contribute to elevated prevalence of suicide attempts among transgender people, such as experiences of harassment, family rejection, housing instability, and discrimination in health care. Over half of those who experienced harassment or bullying in schools reported lifetime suicide attempts, as did 57 percent of those who reported that their family chose not to speak/spend time with them.  High prevalence of suicide attempts was also found among those who had ever experienced homelessness (69%) and those who reported a doctor or healthcare provider refused to treat them (60%).The study utilized data collected through the National Transgender Discrimination Survey (NTDS), which was conducted by the National Center for Transgender Equality and the National Gay and Lesbian Task Force. 6,456 transgender and gender non-conforming people in the United States reported on their experiences of discrimination and abuse at work, at home, in school, and in the public sphere, amassing the largest transgender survey sample to date

Suicide Attempts Among Transgender and Gender Non-Conforming Adults

New analysis of responses to the National Transgender Discrimination Survey (NTDS) shows that transgender respondents who experienced rejection by family and friends, discrimination, victimization, or violence have a higher risk of attempting suicide. 78 percent of survey respondents who suffered physical or sexual violence at school reported suicide attempts, as did 65 percent of respondents who experienced violence at work.The study suggests that several minority stressors – negative experiences related to anti-transgender bias – may contribute to elevated prevalence of suicide attempts among transgender people, such as experiences of harassment, family rejection, housing instability, and discrimination in health care. Over half of those who experienced harassment or bullying in schools reported lifetime suicide attempts, as did 57 percent of those who reported that their family chose not to speak/spend time with them.  High prevalence of suicide attempts was also found among those who had ever experienced homelessness (69%) and those who reported a doctor or healthcare provider refused to treat them (60%).The study utilized data collected through the National Transgender Discrimination Survey (NTDS), which was conducted by the National Center for Transgender Equality and the National Gay and Lesbian Task Force. 6,456 transgender and gender non-conforming people in the United States reported on their experiences of discrimination and abuse at work, at home, in school, and in the public sphere, amassing the largest transgender survey sample to date

Effect of ligand backbone on the selectivity and stability of rhodium hydroformylation catalysts derived from phospholane-phosphites

A study on how ligand backbone structure has an impact on selectivity, rate, and catalyst stability of hydroformylation catalysts was prompted by some longer-term stability issues being discovered for a phospholane-phosphite with a [−CH2O−] backbone. A series of phospholane-phosphite ligands were synthesized. Catalysts made in situ from these ligands and [Rh(acac)(CO)2] were found to give iso-butanal selectivities up to 75% at temperatures between 75 and 105 °C: the latter being a benchmark for iso-selectivity in reactions conducted at industrially meaningful temperatures. A racemic rhodium complex of a bidentate phospholane-phosphite from a tropos-biphenol with an extended backbone showed unusually high stability at high temperatures, combined with even better iso-selectivity in propene hydroformylation relative to the original complex. A related ligand with an electron-withdrawing group maintained the unusually high stability and improved activity. Characterization of the precatalysts of type [RhH(CO)2(L)] was accomplished using in situ HPIR spectroscopy and backed up by density functional theory calculations (B3PW91-D3 level) and by NMR studies; the latter showed that the variation of the backbone also had a pronounced impact on the precatalyst structure. A key finding is that it is now possible to prepare phospholane-phosphite ligands that deliver high iso-butanal selectivity and that show no signs of degradation after several days even above typical reaction temperatures. In one stability test, several kilograms of aldehydes were produced with TOF and selectivity being consistent over several days