Lithiation of carbamates followed by borylation provides a powerful method for the homologation of boron reagents. However, when applied to hindered systems (secondary carbamates with tBu-boronic esters) for the construction of two quaternary centers, this methodology fails. Instead, using mixed boranes (tBuBMe2), the synthesis of adjacent quaternary stereogenic centers with full stereocontrol was successful. The process can be repeated two or three times in one pot leading to carbon chains bearing multiple contiguous quaternary stereogenic centers. The boranes were converted into tertiary alcohols or C-tertiary amines using chloramine. The origin of the high selectivity for alkyl over Me group migration was determined computationally.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1021/ja509029h | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Sc(OTf)-Catalyzed Precise Construction of Medium-Sized [4.2.1]-Oxabridged Scaffolds.
J Org Chem
December 2024
College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, China.
In this study, the readily available and inexpensive Sc(OTf) was utilized to activate ortho-benzoyl diazo compounds to in situ generate highly reactive cyclic 1,3-dipoles, which underwent a regioselective [4 + 3] cycloaddition with dioxopyrrolidines, yielding the [4.2.1]-oxabridged scaffolds bearing multiple contiguous quaternary carbon centers with high diastereoselectivities.
View Article and Find Full Text PDFStrain-release enables access to carbonyl conjugated allylic diborons and alkenyl boronates having multiple contiguous stereocenters in a one-pot process.
Chem Sci
December 2024
Department of Chemistry and Chemical Biology, Stevens Institute of Technology Hoboken NJ 07307 USA
Allylic diboronates are highly valuable reagents in organic synthesis. Existing methods predominantly yield alkyl-substituted allylic diboronates, while the incorporation of electrophilic carbonyl groups conjugated to these allylic systems remains unknown. We present a strain-release promoted cycloaddition-based strategy that enabled access to unprecedented carbonyl conjugated secondary allylic diborons.
View Article and Find Full Text PDFNeighborhood Disadvantage in a Nationally Representative Sample of Community-Living Older US Adults.
JAMA Netw Open
December 2024
Yale School of Public Health, New Haven, Connecticut.
Importance: Although neighborhood socioeconomic disadvantage has become the standard for evaluating contextual socioeconomic deprivation at the Census-block level, little is known about its prevalence or association with long-term mortality in nationally representative samples of older persons.
Objectives: To estimate the prevalence of neighborhood disadvantage among a nationally representative sample of community-living older adults; to identify how prevalence estimates differ based on relevant demographic, socioeconomic, geographic, clinical, and geriatric characteristics; and to evaluate the association between neighborhood disadvantage and all-cause mortality.
Design, Setting, And Participants: This cohort study analyzed linked data of community-living persons aged 65 years or older in the contiguous US participating in the National Health and Aging Trends Study (NHATS) from 2011 to 2021.
The dimensionality of neural coding for cognitive control is gradually transformed within the lateral prefrontal cortex.
J Neurosci
December 2024
MRC Cognition and Brain Sciences Unit, University of Cambridge, UK.
Implementing cognitive control relies on neural representations that are inherently high-dimensional and distributed across multiple subregions in the prefrontal cortex (PFC). Traditional approaches tackle prefrontal representation by reducing it into a unidimensional measure (univariate amplitude) or using them to distinguish a limited number of alternatives (pattern classification). By contrast, representational similarity analysis (RSA) enables flexibly formulating various hypotheses about informational contents underlying the neural codes, explicitly comparing hypotheses, and examining the representational alignment between brain regions.
View Article and Find Full Text PDFCerebellar Involvement in Attacks of Aquaporin-4-IgG Positive Neuromyelitis Optica Spectrum Disorder.
Neurol Neuroimmunol Neuroinflamm
January 2025
From the Department of Neurology and Center for Multiple Sclerosis and Autoimmune Neurology (A.D., L.C., J.J.-W.C., B.G.W., S.A.B., S.J.P., E.P.F.), Mayo Clinic College of Medicine, Rochester, MN; Department of Neurosciences (A.D.), Biomedicine, and Movement Sciences, University of Verona, Italy; Department of Radiology (K.N.K.), Mayo Clinic; Department of Ophthalmology (J.J.-W.C.), Mayo Clinic College of Medicine, Rochester, MN; Department of Neurology (D.M.W., C.V.-S.), Mayo Clinic, Scottsdale, AZ; Department of Neurology (B.G.W.), University of Virginia, Charlottesville; Department of Neurology (A.S.L.-C.), Mayo Clinic College of Medicine, Jacksonville, FL; Neurology Unit (E.S.), University Hospital of Sassari, Italy; and Department of Laboratory Medicine and Pathology (S.J.P., E.P.F.), Mayo Clinic College of Medicine, Rochester, MN.
Objectives: To characterize the frequency and clinicoradiologic phenotype of cerebellar involvement in attacks of aquaporin-4-IgG positive neuromyelitis optica spectrum disorder (AQP4+NMOSD) which are incompletely captured in current diagnostic criteria.
Methods: Brain MRI scans from patients with AQP4+NMOSD in the Mayo Clinic database were reviewed, and those with cerebellar T2-hyperintense lesions ≤30 days from attack onset were included for clinical and radiologic characterization.
Results: From 432 patients with AQP4+NMOSD, we identified 17 (4%) with cerebellar attacks.
Want AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!