MECHANISTIC STUDIES AND APPLICATIONS OF AMINOHALOGENATION OF OLEFINS

Ph.DDOCTOR OF PHILOSOPH

Catalyst-free and metal-free electrophilic bromoamidation of unactivated olefins using the N-bromosuccinimide/sulfonamide Protocol

10.1021/jo502416rJournal of Organic Chemistry8052815-282

An unexpected Bromolactamization of Olefinic Amides Using a Three-Component Co-catalyst System

Reaction between (<i>N</i>,<i>N</i>-dimethylamino)­pyridine and isocyanate unexpectedly produced a three-component mixture. By using this mixture as an unprecedented three-component catalyst system, a facile and selective bromolactamization of olefinic amides has been developed. The protocol confers enhanced selectivity of <i>N</i>- over <i>O</i>-cyclization, leading to the formation of a structurally diverse range of lactams including both small and medium ring sizes

An unexpected Bromolactamization of Olefinic Amides Using a Three-Component Co-catalyst System

Reaction between (<i>N</i>,<i>N</i>-dimethylamino)­pyridine and isocyanate unexpectedly produced a three-component mixture. By using this mixture as an unprecedented three-component catalyst system, a facile and selective bromolactamization of olefinic amides has been developed. The protocol confers enhanced selectivity of <i>N</i>- over <i>O</i>-cyclization, leading to the formation of a structurally diverse range of lactams including both small and medium ring sizes

An unexpected Bromolactamization of Olefinic Amides Using a Three-Component Co-catalyst System

Reaction between (<i>N</i>,<i>N</i>-dimethylamino)­pyridine and isocyanate unexpectedly produced a three-component mixture. By using this mixture as an unprecedented three-component catalyst system, a facile and selective bromolactamization of olefinic amides has been developed. The protocol confers enhanced selectivity of <i>N</i>- over <i>O</i>-cyclization, leading to the formation of a structurally diverse range of lactams including both small and medium ring sizes

Catalyst-Free and Metal-Free Electrophilic Bromoamidation of Unactivated Olefins Using the <i>N</i>‑Bromosuccinimide/Sulfonamide Protocol

An efficient, catalyst-free, and metal-free bromoamidation of unactivated olefins has been developed. 4-(Trifluoromethyl)­benzenesulfonamide and <i>N</i>-bromosuccinimide were used as the nitrogen and halogen sources, respectively. The methodology is applicable to both cyclic and aliphatic olefins

Occurrence and dietary exposure to acrylamide from foods consumed within and outside main meals in Singapore

This study investigated the influence of 'snackification' in Singaporean diets, leading to increased dietary acrylamide exposure. Acrylamide concentrations in commonly consumed foods within and outside the main meals were measured using liquid chromatography with tandem mass spectrometry (LC-MS/MS). High acrylamide concentrations were detected in vegetables cooked at high temperatures (ranging from 0.5 to 478.4 µg/kg) and potato-based crackers and chips (ranging from 81.8 to 2095.8 µg/kg). The estimated total dietary exposure for the Singapore population was 0.165 µg/kg bw/day for general consumers and 0.392 µg/kg bw/day for high consumers (95th percentile). The acrylamide exposure from outside main meals was nearly equivalent to that from within the main meals. The calculated margins of exposure (MOE) were below 10,000, indicating potential human health concern. These findings highlight the need for industry practices and consumer advisories to reduce acrylamide exposure from foods consumed both within and outside main meals.Published versio

Final report of the CCQM-K145: toxic and essential elements in bovine liver

Liver plays a major role in metabolism and acts as a source of energy for the body by storing glycogen. With the growing interest and investigation in the biological effects in recent years, it is important and necessary to develop accurate and comparable analytical methods for elements in bio-samples. It has, however, been 10 years since the tissue sample (bovine liver) of CCQM-K49 key comparison. The purpose of CCQM-K145 is to ensure the comparable and traceable measurement results for essential and toxic elements such as P, S, Zn, Mn, Ni, Mo, Sr, Cr, Co, Pb, As and Hg in bovine liver among NMIs and other designated measurement bodies worldwide. The comparison was agreed by IAWG as 6th IAWG Benchmarking Exercise with Zn and Ni as exemplary elements at the meeting in Korea in the early October 2016. The results of CCQM-K145 are expected to cover the measurement capability and support CMCs claiming for inorganic elements in the similar biological tissue materials and food samples. 30 NMIs and DIs registered in CCQM-K145. With respect to the methodology, a variety of techniques such as IDMS, ICP-OES, ICP-MS(non-ID), AAS and NAA were adopted by the participants. For Zn, Ni, Sr, Pb and Hg measurements, most participants chose ID-ICP-MS method, which showed the better performance in terms of consistency and reliability of the measurement results. In aspect of the traceability for the measurement results in CCQM-K145, most participants used their own (in house) CRMs or other NMI's CRMs to guarantee trace to SI unit. Most participants used similar matrix CRMs for quality control or method validation. Base on different statistic way to calculate the reference mass fraction values and associated uncertainties for each measurand, removal of the suspected extreme values, and discussion at the IAWG meetings, the median values are proposed as the KCRV for Zn, Ni, Mn, Mo, Cr, Pb and Hg; the arithmetic mean values are proposed as the KCRV for P, S, Sr, Co and As. In general, the performances of the majority of CCQM-K145 participants are very good, illustrating their measurement capabilities for Zn, Ni, P, S, Mn, Mo, Sr, Cr, As, Co, Pb and Hg in a complex biological tissue matrix. Bovine liver contains many kinds of nutrients and microelements, it can be regarded as a typical representative material of biological tissue and food. In CCQM-K145, the analytes involved alkali metals and transition elements, metalloids / semi-metals and non metals with a range of mass fraction from mg/g to μg/kg. CCQM-K145 also tested the ability of NMIs/DIs to determine elements that were easy to be lost and polluted, and interfered significantly. The chemical pretreatment methods of samples used in the comparison is suitable for general food and biological matrix samples. A variety of measurement methods used in the comparison represent the main instrumental technology for elemental analysis. Therefore, for supporting CMC claim, CCQM-K145 is readily applicable to measurement of more elements in a wide range of biological materials (including liquids and solids) and meat products