Characterization of Nitrosocarbonyl Compounds by Neutralization-Reionization Mass Spectrometry

Generation and Trapping of Nitrosocarbonyl Intermediates

The nitrosocarbonyls (R-CONO) are highly reactive species and remarkable intermediates toward different synthetic targets. This review will cover a research area whose impact in current organic synthesis is constantly increasing in the chemical community. This review represents the first and comprehensive picture on the generation and trapping of nitrosocarbonyls and is solidly built on more than 380 papers. Six different classes of key starting materials such as hydroxamic acids, N-hydroxy carbamates, N-hydroxyureas, nitrile oxides, and 1,2,4-oxadiazole-4-oxides were highlighted. The content of the review surveys all the methods to generate the nitrosocarbonyls through different approaches (oxidative, thermal, photochemical, catalytic, aerobic, and the less common ones) in the light of efficiency, yields, and mildness. The most successful trapping agents employed to catch these fleeting intermediates are reviewed, exploiting their superior dienophilic, enophilic, and electrophilic power. The work is completed by paragraphs dedicated to the detection of the intermediates, theoretical studies, and insights about the challenges and future directions for the field.

The nitrosocarbonyl hetero-Diels-Alder reaction as a useful tool for organic syntheses

Organic transformations that result in the formation of multiple covalent bonds within the same reaction are some of the most powerful tools in synthetic organic chemistry. Nitrosocarbonyl hetero-Diels-Alder (HDA) reactions allow for the simultaneous stereospecific introduction of carbon-nitrogen and carbon-oxygen bonds in one synthetic step, and provide direct access to 3,6-dihydro-1,2-oxazines. This Review describes the development of the nitrosocarbonyl HDA reaction and the utility of the resulting oxazine ring in the synthesis of a variety of important, biologically active molecules.

Concise syntheses of enantiomerically pure protected 4-hydroxypyroglutamic acid and 4-hydroxyproline from a nitroso-cyclopentadiene cycloadduct

O-TBS-protected methyl trans-4-hydroxypyroglutamate and methyl trans-4-hydroxyproline ester were synthesized from nitroso-cyclopentadiene Diels-Alder cycloadducts. Enzymatic resolution of the key intermediate, 4-amino-cyclopent-2-enol, provides access to both L- and D- amino acids.

Direct observation of an acyl nitroso species in solution by time-resolved IR spectrocopy

Benzoyl nitroside (5) was generated in solution by laser photolysis of 3,5-diphenyl-1,2,4-oxadiazole-4-oxide (4) and studied by time-resolved infrared spectroscopy. The second-order rate constants for reaction of 5 with diethylamine and 1,3-cyclohexadiene were determined to be (1.3 +/- 0.5) x 10(5) M(-1) s(-1) and (6.0 +/- 0.5) x 10(3) M(-1) s(-1), respectively. The formation of nitroxyl (HNO), a product of the reaction of 5 with diethylamine, was also observed.