Ring Expansions of Cyclopropanated Carbohydrates

<p>The combination of cyclopropanes and carbohydrates functionality within a single molecule gives the synthetic chemist an interesting combination of reactivity and chirality to expand further upon. However, until recently relatively little work has been done in this field. Following the report of methodology to convert cyclopropanated carbohydrates into oxepines in high yields, this investigation set out to improve the selectivity of the rearrangement and also investigate the further utility of the subsequent products. Focused investigation of the starting substrates and reaction conditions led to a minor adaptation of the previously successful methodology for the ring expansion of cyclopropanated glycals. This resulted in a substantial increase in the selectivity of the reaction to generate oxepine rings in good to excellent yields with a range of nucleophiles. One of the oxepines was subsequently chosen for elaboration into a range of synthons for further investigations. These yielded a variety of oxepanes in good yields with well defined stereo- and regioselective outcomes. In the course of these reactions several unexpected products were isolated. These were further investigated with labelling experiments and a mechanism for their formation was proposed. Finally the methodology was applied to the total synthesis of a naturally occurring oxepine containing compound. Despite the apparent simplicity of the target, the effort was ultimately unsuccessful.</p>

Ring Expansions of Cyclopropanated Carbohydrates

<p>The combination of cyclopropanes and carbohydrates functionality within a single molecule gives the synthetic chemist an interesting combination of reactivity and chirality to expand further upon. However, until recently relatively little work has been done in this field. Following the report of methodology to convert cyclopropanated carbohydrates into oxepines in high yields, this investigation set out to improve the selectivity of the rearrangement and also investigate the further utility of the subsequent products. Focused investigation of the starting substrates and reaction conditions led to a minor adaptation of the previously successful methodology for the ring expansion of cyclopropanated glycals. This resulted in a substantial increase in the selectivity of the reaction to generate oxepine rings in good to excellent yields with a range of nucleophiles. One of the oxepines was subsequently chosen for elaboration into a range of synthons for further investigations. These yielded a variety of oxepanes in good yields with well defined stereo- and regioselective outcomes. In the course of these reactions several unexpected products were isolated. These were further investigated with labelling experiments and a mechanism for their formation was proposed. Finally the methodology was applied to the total synthesis of a naturally occurring oxepine containing compound. Despite the apparent simplicity of the target, the effort was ultimately unsuccessful.</p>

Encoding stereochemical molecular information on cyclophanes using non-directional interactions and achiral building blocks

The stereoselective assembly of achiral constituents through a single spontaneous process into complex covalent architectures bearing multiple stereogenic elements currently seems out of reach to the synthetic chemist. It even seems beyond what nature itself has managed to attain through evolution. Here, we show that such an extreme level of control can be achieved by molecular programming, i.e. by implementing stereo-electronic information on synthetic organic building blocks and exploiting the features of the covalent reactions and interactions, whose interplay acts as a powerful assembling algorithm. Remarkably, we show that non-directional bonds and interactions can reliably transfer this information, delivering in near to physiological conditions, high-molecular weight macrocyclic species carrying up to 8-bits of conformational and configuration information. Beyond the field of supramolecular chemistry, this proof of concept should stimulate the on-demand production of highly structured polyfunctional architectures.

Mobile Application for Recording the Results of Laboratory Research of a Synthetic Chemist

This article discusses an application for mobile devices with the Android operating system that allows you to record the results of laboratory research of a synthetic chemist. An overview of the basic functionality of the Chemical Notes mobile application is presented.

Information System for Registration of Research Results of a Synthetic Chemist

This article describes the information system, which is an electronic version of the laboratory journal of chemist-synthetics. An overview of the basic functionality of the program is presented.

1.13 Intramolecular Hydrogen-Atom Transfer

Recent advances in intramolecular hydrogen-atom transfer (HAT) have demonstrated significant utility in C—H functionalization through highly reactive open-shell intermediates. The intramolecular transposition of radical reactivity from select functional groups to generate more stable carbon-centered radicals often proceeds with high regioselectivity, providing novel bond disconnections at otherwise inert and largely indistinguishable positions. This chapter explores the functional groups capable of intramolecular HAT to generate remote radicals and the transformations currently available to the synthetic chemist.

Recent advances in Minisci-type reactions and applications in organic synthesis

Abstract:: Minisci-type reactions have become widely known as reactions that involve the addition of carbon-centered radicals to basic heteroarenes followed by formal hydrogen atom loss. While the originally developed protocols for radical generation remain in active use today, in recent years by a new array of radical generation strategies allow use of a wider variety of radical precursors that often operate under milder and more benign conditions. New transformations based on free radical reactivity are now available to a synthetic chemist looking to utilize a Minisci-type reaction. Radical-generation methods based on photoredox catalysis and electrochemistry, which utilize thermal cleavage or the in situ generation of reactive radical precursors, have become popular approaches. Our review will cover the remarkably literature that has appeared on this topic in recent 5 years, from 2015-01 to 2020-01, in an attempt to provide guidance to the synthetic chemist, on both the challenges that have been overcome and applications in organic synthesis.

Cartridge-based Automated Synthesis – A New Tool for the Synthetic Chemist

Despite recent advances in reaction methodologies, organic synthesis remains complex and challenging. Many of the fundamental processes in use have not changed in over 100 years, with a large proportion of the work being carried out manually, using lengthy procedures and difficult or hazardous reaction conditions. As such, organic synthesis still presents a bottle-neck in discovery research. Endeavours to automate synthesis in discovery, through robotic platforms, have so far not been widely successful because the highly complex nature of such machines, and the level of skill required for their operation, presents a barrier too great for most discov- ery chemists. Synple Chem has developed a safe, easy to use, efficiency-enhancing automated technology for the acceleration of discovery research. The automated flow-batch hybrid system utilises a range of innovative pre-packed reagent cartridges for different reaction classes, along with pre-programmed, highly optimised but editable reaction protocols. The combination of these three key elements, provides users with a convenient, easy to use, time-saving technology that makes the synthesis of molecules far simpler, faster and more efficient. The described technology offers all discovery chemists access to real synthesis automation without any of the barriers that have previously restricted its utility.