C=N-containing azaarenes as activating groups in enantioselective catalysis

Nitrogen-containing aromatic heterocycles (azaarenes) are of widespread chemical significance, and chi-ral compounds containing azaarenes feature prominently in pharmaceuticals, agrochemicals, and natural products. This Perspective highlights the use of a relatively underdeveloped strategy to prepare chiral azaarene-containing compounds: exploitation of the C=N bond embedded within certain azaarenes to activate adjacent functionality in catalytic asym-metric reactions. Work in this area has resulted in the development of several different types of catalytic enantioselec-tive processes, including reductions, nucleophilic additions, and reductive couplings. It is hoped that this Perspective will encourage more researchers to work in this promising area

Enantioselective Copper-Catalyzed Reductive Coupling of Alkenylazaarenes with Ketones

Catalytic enantioselective methods for the preparation of chiral azaarene-containing compounds are of high value. By combining the utility of copper hydride catalysis with the ability of C═N-containing azaarenes to activate adjacent alkenes toward nucleophilic additions, the enantioselective reductive coupling of alkenylazaarenes with ketones has been developed. The process is tolerant of a wide variety of azaarenes and ketones, and provides aromatic heterocycles bearing tertiary-alcohol-containing side chains with high levels of diastereo- and enantioselection

Copper-catalyzed borylative coupling of vinylazaarenes and N-Boc imines

Cu-catalyzed three-component couplings of vinylazaarenes, B2(pin)2, and N-Boc imines are described. Oxidation of the initially formed boronate gives azaarene-containing, Boc-protected amino alcohols with reasonable to good diastereoselectivities

Direct Synthesis of 5-Aryl Barbituric Acids by Rhodium(II)-Catalyzed Reactions of Arenes with Diazo Compounds

A commercially available rhodium(II) complex catalyzes the direct arylation of 5‐diazobarbituric acids with arenes, allowing straightforward access to 5‐aryl barbituric acids. Free N--H groups are tolerated on the barbituric acid, with no complications arising from N--H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor

A rubric based approach towards Automated Essay Grading : focusing on high level content issues and ideas

Assessment of a student’s work is by no means an easy task. Even if the student response is in the form of multiple choice answers, manually marking those answer sheets is a task that most teachers regard as rather tedious. The development of an automated method to grade these essays was thus an inevitable step.This thesis proposes a novel approach towards Automated Essay Grading through the use of various concepts found within the field of Narratology. Through a review of the literature, several methods in which essays are graded were identified together with some of the problems. Mainly, the issues and challenges that plague AEG systems were that those following the statistical approach needed a way to deal with more implicit features of free text, while other systems which did manage that were highly dependent on the type of student response, the systems having pre-knowledge pertaining to the subject domain in addition to requiring more computational power. It was also found that while narrative essays are one of the main methods in which a student might be able to showcase his/her mastery over the English language, no system thus far has attempted to incorporate narrative concepts into analysing these type of free text responses.It was decided that the proposed solution would be centred on the detection of Events, which was in turn used to determine the score an essay receives under the criteria of Audience, Ideas, Character and Setting and Cohesion, as defined by the NAPLAN rubric. From the results gathered from experiments conducted on the four criteria mentioned above, it was concluded that the concept of detecting Events as they were within a narrative type story when applied to essay grading, does have a relation towards the score the essay receives. All experiments achieved an average F-measure score of 0.65 and above while exact agreement rates were no lower than 70%. Chi-squared and paired T-test values all indicated that there was insufficient evidence to show that there was any significant difference between the scores generated by the computer and those of the human markers

Rhodium-catalyzed oxidative C–H allylation of benzamides with 1,3-dienes by allyl-to-allyl 1,4-Rh(III) migration

The Rh(III)-catalyzed oxidative C–H allylation of N-acetylbenzamides with 1,3-dienes is described. The presence of allylic hydrogens cis- to the less substituted alkene of the 1,3-diene is important for the success of these reactions. With the assistance of reactions using deuterated 1,3-dienes, a proposed mechanism is provided. The key step is postulated to be the first reported examples of allyl-to-allyl 1,4-Rh(III) migration

Synthesis of spirocyclic enones by rhodium-catalyzed dearomatizing oxidative annulation of 2-alkenylphenols with alkynes and enynes

The dearomatizing oxidative annulation of 2-alkenylphenols with alkynes and enynes proceeds with high yields and regioselectivities under Rh(III) catalysis. These reactions are successful using Cu(OAc)2 or air as the stoichiometric oxidant, and provide spirocyclic enones, the basic ring system of which appears in several natural products. Application of this process to the preparation of a highly functionalized tetracycle is also demonstrated

One-carbon oxidative annulations of 1,3-enynes by catalytic C–H functionalization and 1,4-rhodium(III) migration

Rhodium(III)-catalyzed C-H functionalization-oxidative annulations of aromatic substrates with 1,3-enynes that contain allylic hydrogen atoms cis to the alkyne are described. The key step in these reactions is an alkenyl-to-allyl 1,4-rhodium(III) migration to give electrophilic pi-allylrhodium(III) species. Nucleophilic trapping of these species gives heterocycles such as benzopyrans, isobenzofuranones, and isoindolinones

Nickel?Catalyzed Arylative Cyclizations of Alkyne? and Allene?Tethered Electrophiles using Arylboron Reagents

The use of arylboron reagents in metal-catalyzed domino addition–cyclization reactions is a well-established strategy for the preparation of diverse, highly functionalized carbo- and heterocyclic products. Although rhodium- and palladium-based catalysts have been commonly used for these reactions, more recent work has demonstrated nickel catalysis is also highly effective, in many cases offering unique reactivity and access to products that might otherwise not be readily available. This review gives an overview of nickel-catalyzed arylative cyclizations of alkyne- and allene-tethered electrophiles using arylboron reagents. The scope of the reactions is discussed in detail, and general mechanistic concepts underpinning the processes are described