Michael Addition of P-Nucleophiles to Conjugated Nitrosoalkenes

N-Functionalization of β-aminophosphonates: cytotoxic effects of the new derivatives

β-Aminophosphonates obtained by the Michael addition of primary amines to the double bond of diethyl vinylphosphonate proved to be suitable starting materials (amine components) in the Kabachnik-Fields reaction with formaldehyde and dialkyl phosphites or secondary phosphine oxides to afford N-phosphonylmethyl- and N-phosphinoylmethyl-β-aminophosphonates. On the other hand, the starting aminophosphonates were modified by N-acylation using acid chlorides. The N-acyl products were found to exist in a dynamic equilibrium of two conformers as suggested by the broad NMR signals. At 26 °C, there may be rotation around the N-C axis of the acylamide function. At the same time, low-temperature NMR measurements at -5 °C revealed the presence of two distinct rotamers that could be characterized by 31P, 13C and 1H NMR data. The modified β-aminophosphonic derivatives were subjected to a comparative structure-activity analysis on MDA-MB-231, PC-3, A431 and Ebc-1 tumor cell lines, and in a few cases, significant activity was detected.

Reactivity of ethyl nitrosoacrylate toward pyrrole, indole and pyrrolo[3,2-c]carbazole: an experimental and theoretical study

Nitrosoalkenes react with 8-methyl-1,6-dihydropyrrolo[3,2-c]carbazole to give both 2- and 3-alkylated products via hetero-Diels-Alder reaction followed by the cycloadduct ring-opening. Quantum chemical calculations, at DFT level of theory, were carried out to investigate the regioselectivity of the cycloaddition of ethyl nitrosoacrylate with 1,6-dihydropyrrolo[3,2-c]carbazoles as well as with pyrrole and indole, allowing a more comprehensive analysis of the reactivity pattern of nitrosoalkenes with five-membered heterocycles. Furthermore, theoretical calculations confirmed that ethyl nitrosoacrylate reacts with these heterocycles via a LUMOheterodiene-HOMOdienophile controlled cycloaddition. The reactivity of one of the oxime-functionalized 1,6-dihydropyrrolo[3,2-c]carbazole was explored and a new hexahydropyrido[4',3':4,5]pyrrolo[3,2-c]carbazole system was obtained in high yield via a one-pot, two-step procedure.

Building Up a Piperazine Ring from a Primary Amino Group via Catalytic Reductive Cyclization of Dioximes

Piperazine is one of the most frequently found scaffolds in small-molecule FDA-approved drugs. In this study, a general approach to the synthesis of piperazines bearing substituents at carbon and nitrogen atoms utilizing primary amines and nitrosoalkenes as synthons was developed. The method relies on sequential double Michael addition of nitrosoalkenes to amines to give bis(oximinoalkyl)amines, followed by stereoselective catalytic reductive cyclization of the oxime groups. The method that we developed allows a straightforward structural modification of bioactive molecules (e.g., α-amino acids) by the conversion of a primary amino group into a piperazine ring.

Mild synthesis of isoxazoline derivatives via an efficient [4 + 1] annulation reaction of transient nitrosoalkenes and sulfur ylides

An efficient [4 + 1] annulation between α-bromooximes and sulfur ylides via in situ generation of nitrosoalkenes under mild basic reaction conditions has been developed, providing an expeditious and scalable approach to synthesize biologically interesting isoxazoline derivatives with good to excellent yields.