Formamide Synthesis through Borinic Acid Catalysed Transamidation under Mild Conditions

A highly efficient and mild transamidation of amides with amines co‐catalysed by borinic acid and acetic acid has been reported. A wide range of functionalised formamides was synthesized in excellent yields, including important chiral α‐amino acid derivatives, with minor racemisation being observed. Experiments suggested that the reaction rely on a cooperative catalysis involving an enhanced boron‐derived Lewis acidity rather than an improved Brønsted acidity of acetic acid.Amide bonds are reputedly difficult to activate due to their high resonance stabilization. An unusual mild activation of dimethylformamide and formamide by borinic acid 1 (see scheme), illustrated by a general formylation of a wide range of amines, including chiral α‐amino esters, has been reported.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137604/1/chem201600234-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137604/2/chem201600234_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137604/3/chem201600234.pd

Direct synthesis of amides from nonactivated carboxylic acids using urea as nitrogen source and Mg(NO₃)₂ or imidazole as catalysts

A new method for the direct synthesis of primary and secondary amides from carboxylic acids is described using Mg(NO3)2·6H2O or imidazole as a low-cost and readily available catalyst, and urea as a stable, and easy to manipulate nitrogen source. This methodology is particularly useful for the direct synthesis of primary and methyl amides avoiding the use of ammonia and methylamine gas which can be tedious to manipulate. Furthermore, the transformation does not require the employment of coupling or activating agents which are commonly required

Commande de manipulateurs mobiles robotisés : application au génie civil

Despite the advancements in industrial automation, robotic solutions are not yet commonly used in the civil engineering sector. More specifically, grinding tasks such as asbestos removal, are still performed by human operators using conventional electrical and hydraulic tools. However, with the decrease in the relative cost of machinery with respect to human labor and with the strict health regulations on such risky jobs, robots are progressively becoming credible alternatives to automate these tasks and replace humans.In this thesis, novel surface grinding control approaches are elaborated. The first controller is based on hybrid position-force controller with compliant wrist and a smooth switching strategy. In this controller, the impact force is reduced by the proposed smooth switching between free space and contact modes. The second controller is based on a developed grinding model and an adaptive hybrid position-velocity-force controller. The controllers are validated experimentally on a 7-degrees-of-freedom robotic arm equipped with a camera and a force-torque sensor. The experimental results show good performances and the controllers are promising. Additionally, a new approach for controlling the stability of mobile manipulators in real time is presented. The controller is based on zero moment point, it is tested in simulations and it was able to actively maintain the tip-over stability of the mobile manipulator while moving. Moreover, the modeling and sensors uncertainties are taken into account in the mentioned controllers where observers are proposed. The details of the development and evaluation of the several proposed controllers are presented, their merits and limitations are discussed and future works are suggested.Malgré le progrès de l'automatisation industrielle, les solutions robotiques ne sont pas encore couramment utilisées dans le secteur du génie civil. Plus spécifiquement, les tâches de ponçage, telles que le désamiantage, sont toujours effectuées par des opérateurs humains utilisant des outils électriques et hydrauliques classiques. Cependant, avec la diminution du coût relatif des machines par rapport au travail humain et les réglementations sanitaires strictes applicables à des travaux aussi risqués, les robots deviennent progressivement des alternatives crédibles pour automatiser ces tâches et remplacer les humains.Dans cette thèse, des nouvelles approches de contrôle de ponçage de surface sont élaborées. Le premier contrôleur est un contrôleur hybride position-force avec poignet conforme. Il est composé de 3 boucles de commande, force, position et admittance. La commutation entre les commandes pourrait créer des discontinuités, ce qui a été résolu en proposant une commande de transition. Dans ce contrôleur, la force de choc est réduite par la commande de transition proposée entre les modes espace libre et contact. Le second contrôleur est basé sur un modèle de ponçage développé et un contrôleur hybride adaptatif position-vitesse-force. Les contrôleurs sont validés expérimentalement sur un bras robotique à 7 degrés de liberté équipé d'une caméra et d'un capteur de force-couple. Les résultats expérimentaux montrent de bonnes performances et les contrôleurs sont prometteurs. De plus, une nouvelle approche pour contrôler la stabilité des manipulateurs mobiles en temps réel est présentée. Le contrôleur est basé sur le « zero moment point », il a été testé dans des simulations et il a été capable de maintenir activement la stabilité de basculement du manipulateur mobile tout en se déplaçant. En outre, les incertitudes liées à la modélisation et aux capteurs sont prises en compte dans les contrôleurs mentionnés où des observateurs sont proposés.Les détails du développement et de l'évaluation des différents contrôleurs proposés sont présentés, leurs mérites et leurs limites sont discutés et des travaux futurs sont suggérés

Correction: Borinic acid catalysed peptide synthesis

International audienc

Boronic acid catalysed peptide synthesis

International audienc

Borinic acid catalysed peptide synthesis

International audienceThe catalytic synthesis of peptides is a major challenge in the modern organic chemistry hindered by the well-established use of stoichiometric coupling reagents. Herein, we describe for the first time that borinic acid is able to catalyse this reaction under mild conditions with an improved activity compared to our recently developed thiophene-based boronic acid. This catalyst is particularly efficient for peptide bond synthesis affording dipeptides in good yields without detectable racemization

Catalytic Chemical Amide Synthesis at Room Temperature: One More Step Toward Peptide Synthesis

International audienceAn efficient method has been developed for direct amide bond synthesis between carboxylic acids and amines via (2-(thiophen-2-ylmethyl)phenyl)boronic acid as a highly active bench-stable catalyst. This catalyst was found to be very effective at room temperature for a large range of substrates with slightly higher temperatures required for challenging ones. This methodology can be applied to aliphatic, α-hydroxyl, aromatic, and heteroaromatic acids as well as primary, secondary, heterocyclic, and even functionalized amines. Notably, N-Boc-protected amino acids were successfully coupled in good yields with very little racemization. An example of catalytic dipeptide synthesis is reported

A Unified Mobile Manipulator Control for On-line Tip-over Avoidance Based on ZMP Disturbance Observer*

International audienceIntroducing mobile manipulators into large working areas has gained importance in the last years. This is due to the fact that manipulators mounted on vehicles have many merits over the ones with fixed bases. The extended workspace and the maneuverability are main advantages of mobile manipulators. However, stability of the system is critical and closely related to the vehicle's motion, arm's motion and the disturbances which may cause the system to tumble. To address the above issue, this paper presents a novel unified dynamic control that keeps the zero moment point (ZMP) on a desired stable position without affecting the end-effector's motion. A redundant scheme is used to develop the motion controller and a novel ZMP disturbance observer is derived to estimate the modeling and inertial errors of the zero moment point to be controlled. Finally, the performance of the proposed controller is validated through dynamic simulation on a 7-dof anthropomorphic arm fixed on differential mobile base. The overall controller not only ensures a good ZMP control for stability but it is also devised to control the end-effector to follow accurately a desired spatial trajectory

A Smooth Position-Force Controller for Asbestos Removal Manipulator

International audience—In robotic grinding tasks, the robot controller must reactively adapt to sudden changes in the environment and be able to handle uncertainties in texture, change in materials, and disturbances caused by vibrations, impacts and friction of the grinding tool operating at high rotational speed. This requires managing sudden signal changes in sensor data. In this paper, we present a smooth hybrid force/position controller based on distance measurements from radars, enabling the robot to achieve a stable interaction with the environment while grinding an unknown three-dimensional surface. The control uses an actively compliant wrist that maintains a desired force centered on the disc and normal to the surface. Our controller is based on a smooth transition between free space and contact modes, significantly reducing the impact force. Additionally, the vibro-dynamic effects are suppressed and smooth environmental tracking is ensured by the impedance/admittance control of the wrist. This framework is validated on a 6-dof anthropomorphic arm through dynamic simulation. The controller is able to adapt reactively to abrupt disturbances in the environment (ex: sudden impacts on the disc) while ensuring good position and force tracking performance