Rules of Chemospecificity of Nucleophilc Ring-opening of Dithia-/Oxathia-Phospholane Towards the Selective Synthesis of Nucleoside 5’-O-Pα-Thio/Dithio/Trithio-Phosphate Ester Conjugates

DBU-assisted nucleophilic ring-opening of both uridine-5’-(2-thio-1,3,2-dithia-phospholane), 3, and uridine-(2-thio-1,3,2-oxathia-phospholane), 8, lasted 2 min at RT and resulted in quantitative yields of uridine-5’-phosphoro-di/trithioate esters. Furthermore, it was selective for alcohol and thiol vs. amine nucleophiles. Yet, reaction of mercaptoethanol with 3, was chemo-specific for the oxygen vs. sulfur nucleophile, while for the reaction of mercaptoethanol with 8, the opposite chemo-specificity was observed, probably related to the steric hindrance in the former case. The observed chemospecificity opens facile avenue for the synthesis of nucleoside-5’-O-Pα-thio/dithio/trithio-phosphate ester derivative

Chiral Porous Carbon Surfaces for Enantiospecific Synthesis

Chiral surfaces, developed in the last decade, serve as media for enantioselective chemical reactions. Until today, they have been based mostly on developments in silica templating, and are made mainly from imprints of silicate materials developed a long time ago. Here, a chiral porous activated carbon surface was developed based on a chiral ionic liquid, and the surface chemistry and pore structure were studied to lay a new course of action in the field. The enantioselectivities of surfaces are examined by using variety of methods such as circular dichroism, linear sweep voltammetry and catalysis. These techniques revealed a 28.1% preference for the D enantiomer of the amino acid proline, and linear sweep voltammetry confirmed chirality recognition by another probe. An aldol surface chiral catalytic reaction was devised and allowed to determine the root of the enantiomeric excess. These results affirm the path toward a new type of chiral surface

A Stereodivergent Approach to the Synthesis of gem-Diborylcyclopropanes

We report a novel designed stereodivergent strategy for the synthesis of gem-diborylcyclopropnes. The reaction provides a highly modular approach to prepare cyclopropane ring variants bearing gem-(Bpin,Bpin), gem-(Bpin,Bdan), and gem-(Bpin,BF3K), with outstanding levels of stereocontrol. This was achieved by diastereoselective Pd-catalyzed cyclopropanation reactions of gem-diborylalkenes with α-diazoarylacetates and α-diazoaryl-trifluoromethyl. The key to the success of this general protocol was the diastereoselective trifluorination reaction of gem-diborylcyclopropanes, followed by the stereospecific interconversion of the trifluoroborate salts into the Bdan group

Stereoselective Diels-Alder Reactions of gem-Diborylalkenes: Toward the Synthesis of gem-Diboron-Based Polymers via ROMP

Although gem-diborylalkenes are known to be among the most valuable reagents in modern organic synthesis, providing a rapid access to a wide array of transformations, including the construction of C−C and C‐heteroatom bonds, their use as dienophile-reactive groups has been rare. Herein we report the Diels-Alder (DA) reaction of (unsymmetrical) gem-diborylalkenes. These reactions provide a general and efficient method for the stereoselective conversion of gem-diborylalkenes to rapidly access 1,1-bisborylcyclohexenes. Using the same DA reaction manifold with borylated-dienes and gem-diborylalkenes, we also developed a concise, highly regioselective synthesis of 1,1,2-tris- and 1,1,3,4-tetrakis(boronates)cyclohexenes, a family of compounds that currently lack efficient synthetic access. Furthermore, DFT calculations provided insight into the underlying factors that control the chemo-, regio, and stereoselectivity of these DA reactions. This method also provides stereodivergent syntheses of gem-diboryl-norbornenes. The utility of the gem-diboryl-norbornene building blocks was demonstrated by ring-opening metathesis polymerization (ROMP), providing a highly modular approach to the first synthesis of the gem-diboron-based polymers. Given its simplicity and versatility, we believe that this novel DA and ROMP approach holds great promise for organoboron synthesis as well as organoboron-based polymers and that it will result in more novel transformations in both academic and industrial research.<br /

Stereocontrolled Radical Thiophosphorylation

The first practical, fully stereoselective P(V)-radical hydrophosphorylation is presented herein using simple, limonene-derived reagent systems. A set of reagents has been developed that upon radical initiation react smoothly with olefins and other radical acceptors to generate P-chiral products which can be further diversified (with conventional 2e- chemistry) to a range of underexplored bioisosteric building blocks. The reactions have a wide scope with excellent chemoselectivity and the unexpected stereochemical outcome has been supported computationally and experimentally. Initial ADME studies are suggestive of the promising properties of this rarely explored chemical space