Reaktionen CH-aktiver Verbindungen mit Aziden, XXVIII1) Synthese α.β-ungesättigter Diazoketone durch entformylierende Diazogruppen-Übertragung

One-pot synthesis of β-O-4 lignin models via the insertion of stable 2-diazo-1,3-dicarbonyls into O-H bonds

Because lignin is a macromolecule that is a sustainable source of aromatic compounds, model substrates are commonly used to increase our understanding of its complex structure. However, few methods have been described for the synthesis of these models. Herein, we describe a new route towards the synthesis of β-O-4 lignin models by intermolecular O-H insertion reactions with simple and stable diazocarbonyls. The benefits of this developed method were shorter reaction times and high yields, as well as mild and environmentally friendly conditions.

α,β-Unsaturated diazoketones as useful platforms in the synthesis of nitrogen heterocycles

Among the different types of diazocarbonyl substrates found in the literature to date, α,β-unsaturated diazoketones have proven to be very promising as multifunctional intermediates. Possessing a diazo group, a ketone function and a double bond all together in a single molecule, these compounds constitute versatile building blocks for synthesis. For example, double bond functionalization, followed by intramolecular insertion reactions, can be a short alternative to prepare several rings or heterocyclic compounds. Although there are many efficient methods to prepare diazoketones, very few can be extended to the synthesis of the a,β-unsaturated diazoketones; this is likely responsible for their limited application in synthesis. Unfortunately, the classical methods to prepare saturated- or aryl-diazoketones (acylation of diazomethane with acyl chlorides or mixed anhydrides) are not suitable for preparing a,β-unsaturated diazoketones, since pyrazolines (dipolar cycloaddition products from the reaction between diazomethane and the double bond) are formed. Although Danheiser's two-step detrifluoroacetylative procedure (starting from a,β-unsaturated methyl ketones) is considered the best general method, it cannot be applied to the synthesis of all types of a,β-unsaturated diazoketones. For example, the synthesis of more complex unsaturated diazoketones, as well as those with epimerizable stereocenters in the γ position, was never described before. Another point is related to the geometry of the double bond, since practically all examples described thus far refer to unsaturated diazoketones with E geometry. In recent years, our research group developed two new Horner-Wadsworth-Emmons reagents (containing a diazocarbonyl function) that could be easily applied in the one-step preparation of α,β-unsaturated diazoketones from aldehydes. Not only were we able to selectively synthesize E- and Z-unsaturated diazoketones, but also to employ these useful platforms in the short synthesis of several nitrogen heterocycles such as indolizidines, quinolizidines, piperidines, and pyrrolidines. Our purpose in this Account is to introduce this class of diazoketone and provide a brief historical overview, culminating in how we developed a general methodology to prepare them. In continuation, we wish to call of the reader's attention to these important building blocks, showing how we could apply them to the synthesis of several nitrogen heterocycles, including the very short preparation of some popular alkaloids. The reader will also notice that the combination of these three important functions in the same molecule makes these compounds special as well as provides powerful platforms to access many important molecules in a direct fashion.

Preparation, spectroscopic properties, and ion chemistry of 3-diazo-1,1,1-trifluoro-2-propanone

The title compound (1) is prepared in satisfactory yield by reacting CH2N2 with trifluoroacetic anhydride in Et2O; the d-analog was obtained by exchange with D2O. 1H, 13C, 15N, 17O, and 19F NMR spectra of 1 were studied, as well as its IR spectrum. A single isomer is present corresponding to the more stable Z configuration. The structural assignment was made on the basis of quantum mechanical calculations, which revealed that the Z form is some 13.4 kJ mol−1 more stable than the E form and the activation energy for the E → Z transition is 64.2 kJ mol−1. Mass spectra under different experimental conditions were recorded and breakdown pathways of the parent ion of 1 charted. Key words: 3-diazo-1,1,1-trifluoro-2-propanone; 3-d-3-diazo-1,1,1-trifluoro-2-propanone; structure; 1H, 13C, 15N, 17O, and 19F NMR; EI-MS.

Evaluation of nuclear-substituted styryl ketones and related compounds for antitumor and cytotoxic properties

A number of nuclear-substituted styryl ketones, the related Mannich bases, and allyl alcohols were synthesized and evaluated for antitumor activity, principally in the L-1210 lymphoid leukemia and P-388 lymphocytic leukemia screening tests. The cytotoxicity of some of these compounds assessed in Eagle's 9KB carcinoma cell culture system was also recorded. Two of the Mannich bases showed promising levels of activity in the P-388 screening; of the results obtained to date, over one-third of the derivatives showed cytotoxicity at dose levels of 1-3 ppm. Other pharmacological results of these compounds are briefly reported.