The heterogeneous reactions of benzo[a]pyrene-d12 (BaP-d12), benzo[k]fluoranthene-d12 (BkF-d12), benzo[ghi]perylene-d12 (BghiP-d12), dibenzo[a,i]pyrene-d14 (DaiP-d14), and dibenzo[a,l]pyrene (DalP) with NO2, NO3/N2O5, and OH radicals were investigated at room temperature and atmospheric pressure in an indoor Teflon chamber and novel mono NO2-DaiP, and mono NO2-DalP products were identified. Quartz fiber filters (QFF) were used as a reaction surface and the filter extracts were analyzed by GC/MS for nitrated-PAHs (NPAHs) and tested in the Salmonella mutagenicity assay, using Salmonella typhimurium strain TA98 (with and without metabolic activation). In parallel to the laboratory experiments, a theoretical study was conducted to rationalize the formation of NPAH isomers based on the thermodynamic stability of OH-PAH intermediates, formed from OH-radical-initiated reactions. NO2 and NO3/N2O5 were effective oxidizing agents in transforming PAHs to NPAHs, with BaP-d12 being the most readily nitrated. Reaction of BaP-d12, BkF-d12 and BghiP-d12 with NO2 and NO3/N2O5 resulted in the formation of more than one mono-nitro isomer product, while the reaction of DaiP-d14 and DalP resulted in the formation of only one mono-nitro isomer product. The direct-acting mutagenicity increased the most after NO3/N2O5 exposure, particularly for BkF-d12 in which di-NO2-BkF-d10 isomers were measured. The deuterium isotope effect study suggested that substitution of deuterium for hydrogen lowered both the direct and indirect acting mutagenicity of NPAHs and may result in an underestimation of the mutagencity of the novel NPAHs identified in this study.
The diboration of ketones with the (ICy)CuOt-Bu catalyst was developed to provide access to tertiary alpha-hydroxyboronate esters. The (ICy)CuOt-Bu catalyst was generated in situ with (ICy)CuCl and NaOt-Bu to afford a more efficient catalyst than the preformed (ICy)CuOt-Bu. These conditions result in the diboration of various ketones in toluene at 50 degrees C in 2-22 h. Treatment of the resulting products with silica gel affords the corresponding alpha-hydroxyboronate esters.
The copper-catalyzed diboration of
ketones followed by an acid-catalyzed
elimination leads to the formation of 1,1-disubstituted and trisubstituted
vinyl boronate esters with moderate to good yields and selectivity.
Addition of tosic acid to the crude diboration products provides the
corresponding vinyl boronate esters upon elimination. The trisubstituted
vinyl boronate esters are formed as the (Z)-olefin
isomer, which was established by subjecting the products to a Suzuki–Miyaura
coupling reaction to obtain alkenes of known geometry.
The copper-catalyzed diboration of
aldehydes was used in conjunction
with the Matteson homologation, providing the efficient synthesis
of β-hydroxyboronate esters. The oxygen-bound boronate ester
was found to play a key role in mediating the homologation reaction,
which was compared to the α-hydroxyboronate ester (isolated
hydrolysis product). The synthetic utility of the diboration/homologation
sequence was demonstrated through the oxidation of one product to
provide a 1,2-diol.
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