排序方式: 共有47条查询结果,搜索用时 0 毫秒
31.
[chemical reaction: see text]. A direct and general synthesis of alpha-branched aldehydes and their enol derivatives is described. Carbocupration of terminal alkynes and subsequent oxygenation with lithium tert-butyl peroxide generates a metallo-enolate. Trapping with various electrophiles provides alpha-branched aldehydes or stereo-defined trisubstituted enol esters or silyl ethers. The tandem carbocupration/oxygenation tolerates alkyl and silyl ethers, esters, and tertiary amines. The reaction is effective with organocopper complexes derived from primary, secondary, and tertiary Grignard reagents and from n-butyllithium. 相似文献
32.
Melissa Moss Xinping Han Prof. Joseph M. Ready 《Angewandte Chemie (International ed. in English)》2016,55(34):10017-10021
Organozirconocenes are versatile synthetic intermediates that can undergo carbonylation to yield acyl anion equivalents. Zirconocene hydrochloride ([Cp2ZrHCl]) is often the reagent of choice for accessing these intermediates but generates organozirconocenes only from alkenes and alkynes. This requirement eliminates a broad range of substrates. For example, organozirconocenes in which the zirconium center is bonded to an aromatic ring, a benzylic group, or an alkyl group that possesses a tertiary or quaternary carbon atom α to the carbon–zirconium bond can not be formed in this way. To provide more generalized access to acyl zirconium reagents, we explored the transmetalation of Grignard reagents with zirconocene dichloride under a CO atmosphere. This protocol generates acyl zirconium(IV) complexes that are inaccessible with the Schwartz reagent, including those derived from secondary and tertiary alkyl and aryl Grignard reagents. 相似文献
33.
Gregory MA Hong H Lill RE Gaisser S Petkovic H Low L Sheehan LS Carletti I Ready SJ Ward MJ Kaja AL Weston AJ Challis IR Leadlay PF Martin CJ Wilkinson B Sheridan RM 《Organic & biomolecular chemistry》2006,4(19):3565-3568
The function of gene products involved in the biosynthesis of the clinically important polyketide rapamycin were elucidated by biotransformation and gene complementation. 相似文献
34.
Vinyl, aryl, and alkynyl organometallics add to ketones containing a stereogenic sulfoxide. Tertiary alcohols are generated in diastereomerically and enantiomerically pure form. Reductive lithiation converts the sulfoxide into a variety of useful functional groups. 相似文献
35.
36.
Cai F Pu X Qi X Lynch V Radha A Ready JM 《Journal of the American Chemical Society》2011,133(45):18066-18069
We demonstrate that allenes, chiral 1,2-dienes, appended with basic functionality can serve as ligands for transition metals. We describe an allene-containing bisphosphine that, when coordinated to Rh(I), promotes the asymmetric addition of arylboronic acids to α-keto esters with high enantioselectivity. Solution and solid-state structural analysis reveals that one olefin of the allene can coordinate to transition metals, generating bi- and tridentate ligands. 相似文献
37.
We report paraelectric resonance absorption measurements on KBr:Li+ as a function of hydrostatic pressure for frequencies in the range 50– 220 GHz. The lines of the spectra separate into two distinct groups. In one case the zero field splittings increase rapidly with pressure (approx. 0.2 GHz/bar) while the effective electric dipole moment decreases rapidly. For the other, the zero field splittings increase 3–4 times more slowly and the dipole moments appear to be converging to a non zero value. Suprisingly, one of the effective dipole moments is increasing with pressure. 相似文献
38.
Koeniger SL Talaty N Luo Y Ready D Voorbach M Seifert T Cepa S Fagerland JA Bouska J Buck W Johnson RW Spanton S 《Rapid communications in mass spectrometry : RCM》2011,25(4):503-510
A new quantitation method for mass spectrometry imaging (MSI) with matrix-assisted laser desorption/ionization (MALDI) has been developed. In this method, drug concentrations were determined by tissue homogenization of five 10 μm tissue sections adjacent to those analyzed by MSI. Drug levels in tissue extracts were measured by liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS). The integrated MSI response was correlated to the LC/MS/MS drug concentrations to determine the amount of drug detected per MSI ion count. The study reported here evaluates olanzapine in liver tissue. Tissue samples containing a range of concentrations were created from liver harvested from rats administered a single dose of olanzapine at 0, 1, 4, 8, 16, 30, or 100 mg/kg. The liver samples were then analyzed by MALDI-MSI and LC/MS/MS. The MALDI-MSI and LC/MS/MS correlation was determined for tissue concentrations of ~300 to 60,000 ng/g and yielded a linear relationship over two orders of magnitude (R(2) = 0.9792). From this correlation, a conversion factor of 6.3 ± 0.23 fg/ion count was used to quantitate MSI responses at the pixel level (100 μm). The details of the method, its importance in pharmaceutical analysis, and the considerations necessary when implementing it are presented. 相似文献
39.
The eels of LiF has been measured in the range 0–18 eV with primary beam energies 50 eV and 1.5 keV. Four peaks are clearly resolved in the band gap region at room temperature. The amplitude of the three lower energy loss peaks was found to depend on beam exposure and temperature. It is concluded that the lowest energy peak arises at a beam induced defect, that the next two peaks arise in lithium metal liberated by the electron beam and that the peak nearest to the band edge is due to an intrinsic surface excitation. 相似文献
40.
Santanu Panda Aaron Coffin Q. Nhu Nguyen Dr. Dean J. Tantillo Prof. Joseph M. Ready 《Angewandte Chemie (International ed. in English)》2016,55(6):2205-2209
When activated by an acylating agent, pyridine boronic esters react with organometallic reagents to form a dihydropyridine boronic ester. This intermediate allows access to a number of valuable substituted pyridine, dihydropyridine, and piperidine products. 相似文献