Lithiierung und elektrophile Substitution an α-Methylengruppen von Nitrosaminen Umpolung der Reaktivität sekundärer Amine

An Organic Chemist's Guide to N-Nitrosamines: Their Structure, Reactivity, and Role as Contaminants

N-Nitrosamines are a class of compounds notorious both for the potent carcinogenicity of many of its members and for their widespread occurrence throughout the human environment, from air and water to our diets and drugs. Considerable effort has been dedicated to understanding N-nitrosamines as contaminants, and methods for their prevention, remediation, and detection are ongoing challenges. Understanding the chemistry of N-nitrosamines will be key to addressing these challenges. To facilitate such understanding, we focus in this Perspective on the structure, reactivity, and synthetic applications of N-nitrosamines with an emphasis on alkyl N-nitrosamines. The role of N-nitrosamines as water contaminants and the methods for their detection are also discussed.

Recent advances in the chemistry of metallated azetidines

The almost unexplored four-membered azetidines represent a particularly interesting class of molecules, among the family of saturated nitrogen heterocycles. This review reports recent developments in direct metal-based functionalization of the azetidine ring, focusing on the regio- and stereoselectivity of these reactions.

Lithiation-electrophilic substitution of N-thiopivaloylazetidine

The fourth protocol: the rarely studied N-thiopivaloyl group plays a crucial role in mediating efficient α lithiation and incorporation of diverse electrophiles onto an azetidine ring; in the presence of chiral ligands, this chemistry also provides the first example of an enantioselective electrophilic substitution on a four-membered ring.

Oxidative Mannich Reaction ofN-Carbobenzyloxy Amines with 1,3-Dicarbonyl Compounds

Efficient carbon-carbon bond formation at the alpha-position of nitrogen was established by one-pot oxidative Mannich reaction of N-carbobenzyloxy (Cbz) amines with 1,3-dicarbonyl compounds using N-tert-butylbenzenesulfinimidoyl chloride as an oxidant.

Asymmetric transformation of N-nitrosamines by inclusion crystallization with optically active hosts

Several N-nitrosopiperidines with chirality solely due to a hindered rotation about the N-N bond were resolved to enantiomers by inclusion crystallization with optically active diols (TADDOLs). The absolute configuration of the guest nitrosamines was deduced from the X-ray crystal structures of the inclusion complexes. The enclathrated nitrosamines were liberated by a competitive complexation of the host diols with piperazine. The optical activity of the resolved nitrosamines is manifested by their CD spectra. A simple chirality rule was proposed for a rationalization of the observed Cotton effect sign corresponding to the n-pi* electronic transition. The optically active nitrosamines are configurationally labile compounds and gradually racemize in solution but they are indefinitely stable in the solid state. The first-order kinetics of the racemization in solution allowed us to assign the N-N rotation barriers by simple polarimetric measurements.

Silicon-Mediated Organic Synthesis

Organic chemists have used the chemical properties of tetracovalent silicon in a remarkable variety of new synthetic transformations. In carbon-functional silanes, exceptional stabilization is provided to a carbocation center in the beta position when the carbon-silicon bond lies in plane. This phenomenon directs electrophilic attack to the silicon-substituted carbon in aryl-, vinyl-, and alkynylsilanes and to carbon-3 in allylsilanes. For different reasons, silicon also stabilizes a carbon-metal bond in the alpha position. Consequently, access to many silicon-containing organometallics is readily available. The exceptional strength of silicon-oxygen and silicon-fluorine bonds is yet another factor that controls the chemical reactivity of silicon reagents. In recent developments, preparative chemists have taken advantage of these properties in imaginative and useful ways.