Benzyl chloride and its derivatives are efficiently deprotonated with strong bases to form αchlorocarbanions. These anions are long-lived enough to enter VNS reactions with nitroarenes or nitroheteroarenes to give a variety of unsymmetrical o-and p-nitrodiarylmethanes. Selectivity of the reaction can be controlled to some extent by changing metal counterions of the base.

Carbenes play a key role in a plethora of organic transformations. Although stabilized diazo carbonyl compounds predominate as a source of electrophilic carbenes, the hazardous nature of nonstabilized analogues calls for their in situ generation from stable precursors. Among these, 1,3,4-oxadiazolines serve as diazoalkane surrogates under UV light irradiation. In view of their high stability, diverse reactivities, and straightforward synthesis, milder methodologies for the activation of these compounds that permit the use of UV-light-sensitive substrates are highly valued. Herein, we report the visible-light-induced activation of oxadiazolines by triplet energy transfer catalysis that, in contrast to UVinduced processes, alters their reactivity and enables the generation of carbenes. The formed reactive species react with electron-poor olefins, thereby giving valuable spirocyclopropanes. Mechanistic investigations, both theoretical and experimental, uncover plausible pathways and highlight the importance of the triplet energy transfer steps.

Reductive aminations of ferrocenecarboxaldehyde, ansa-ferrocenecarboxaldehyde, and 1,1'-ferrocene-dicarboxaldehyde with allylamine, N-allylmethylamine, or N-allylaniline were investigated. In the case of the dialdehyde only one formyl group effectively reacted with N-allylmethylamine or N-allylaniline, thus providing a simple route to aminomethyl aldehydes and aminomethyl alcohol. 2-Aza-ansa[3] ferrocene was also obtained by reacting the dialdehyde with one equivalent of allylamine and subsequent deprotection of the nitrogen atom. The isolated N-allyl ferrocene derivatives were completely characterized by spectroscopic techniques, whereas crystal structures of four representative compounds were determined using single-crystal X-ray diffraction. MTT assays showed that these simple N-allyl ferrocene derivatives display anticancer activity (MCF-7, A-549 and PC-3 cell lines) in the micromolar range.