Gold-Catalyzed Synthesis of 2-Aryl-3-fluoropyrroles
摘要:
The gold-catalyzed cyclization and dehydrofluorination of gem-difluorohomopropargylamines provides a novel access to 2-aryl-3-fluoropyrroles. Difluorinated homopropargylamines are prepared by the addition of gem-difluoropropargyllithium reagents to arylated N-tosylimines.
Nucleophilic and electrophilic substitutions of difluoropropargyl bromides
作者:Gerald B. Hammond
DOI:10.1016/j.jfluchem.2005.12.024
日期:2006.5
electrophilically substituted difluoropropargyl derivatives via magnesium and fluoride promoted reactions. An indium-mediated reaction of silyldifluoropropargyl bromide, followed by electrophilic trapping with bromine led to a very useful bromoallene, which was then used in reactions with nucleophiles (C, O, N, P, S, Hal) to yield a de facto bimolecular nucleophilic substitution of a difluoropropargyl
An integrated fully differential CMOS transimpedance amplifier (TIA) with buried double junction photodiode input is described. The TIA features a variable high transimpedance gain (250 kΩ to 2.5 MΩ), large DC photocurrent rejection capability (>55 dB) and low input referred noise density at 100 kHz (2pA/√Hz).
Lanthanide Triflate-Catalyzed Preparation of β,β-Difluorohomopropargyl Alcohols in Aqueous Media. Application to the Synthesis of 4,4-Difluoroisochromans
作者:Satoru Arimitsu、Gerald B. Hammond
DOI:10.1021/jo0614588
日期:2006.10.1
An indium-mediated Barbier-type reaction of difluoropropargyl bromide with several aldehydes in aqueous media was enhanced by a catalytic amount of a lanthanide triflate (5 mol %). The reaction gave the corresponding beta,beta-difluorohomopropargyl alcohols with high regioselectivity. The [2 + 2 + 2] alkyne cyclotrimerization of beta,beta-difluorohomopropargyl alcohols with monosubstituted acetylenes produced 4,4-difluoroisochromans in good yields with moderate regioselectivity.
Highly Regioselective Synthesis of <i>gem</i>-Difluoroallenes through Magnesium Organocuprate S<sub>N</sub>2‘ Substitution
作者:Masayuki Mae、Jiyoung A. Hong、Bo Xu、Gerald B. Hammond
DOI:10.1021/ol052816g
日期:2006.2.1
[GRAPHICS]The reaction of gem-difluoropropargyl electrophiles with Grignard reagents is complicated by the inherent difficulty of executing nucleophilic substitutions on a CF2 group, and the facile formation of carbenoid intermediates arising from alpha-elimination of fluoride. In the presence of an excess amount of a copper salt, a Grignard reagent reacts with gem-difluoropropargyl bromide via an SINT mechanism to produce gem-difluoroallene in high yield. If desired, the resulting difluoroallene can undergo a second nucleophilic attack on the CF2 terminus to yield a trisubstituted monofluoroallene through an addition-elimination mechanism.
Stereoselective Functionalization of Racemic Cyclopropylzinc Reagents via Enantiodivergent Relay Coupling
作者:Lun An、Fei-Fei Tong、Shu Zhang、Xingang Zhang
DOI:10.1021/jacs.0c04462
日期:2020.7.8
cyclopropylzinc reagents. This strategy relies on a one-pot, two-step enantiodivergent relay coupling (EDRC) process of the racemic cis-cyclopropylzinc reagents with two different electrophiles, which involves kinetic resolution of racemic cis-cyclopropylzinc reagents through a nickel-catalyzed enantioselective coupling with alkyl electrophiles, followed by a stereospecific relay coupling of the remaining