The title salt, C24H24N(+)·BF4 (-), is one of two possible dias-tereoisomers having a different configuration of the asymmetric centre in the α-phenyl-ethyl substituent, whose absolute configuration was established to be R. The two phenyl substituents of the cation have a cofacial orientation, albeit with a long centroid-centroid separation of 4.129 (3) Å. The crystal structure exhibits numerou...

A stereoselective N-iminium ion cyclization with allylsilane to construct vicinal quaternary-tertiary carbon centers was developed for the concise synthesis of (±)-cephalotaxine. The current strategy features a TiCl4-promoted cyclization and ring-closure metathesis to furnish the spiro-ring system. The stereochemical outcome in the N-acyliminium ion cyclization was rationalized by the stereoele...

In the title salt, C6H14NO(+)·C2H5SO4 (-), the C-N bond lengths in the cation are 1.2981 (14), 1.4658 (14) and 1.4707 (15) Å, indicating double- and single-bond character, respectively. The C-O bond length of 1.3157 (13) Å shows double-bond character, indicating charge delocalization within the NCO plane of the iminium ion. In the crystal, C-H⋯O hydrogen bonds between H atoms of the cations and...

A microwave-assisted, multicomponent protocol for the synthesis of substituted 3,4-dihydroquinazolinones via a novel cascade imine/cyclization/aza-Henry reaction sequence is reported. Starting from o-formyl carbamates, a series of structurally diverse 3,4-dihydroquinazolinones was synthesized via a cyclic iminium ion intermediate in moderate to excellent yields. Notably, the reaction is fast, f...

Within the realm of catalytic asymmetric hydrogenation, the focus continues to be on the use of chiral metal complexes in conjunction with a hydrogen source. Recently, the widespread development of organocatalysis, including the invention of iminium activation, has led to the discovery of many new enantioselective transformations. Based on this strategy, a number of bioinspired processes for th...

In this paper we describe new multi-catalysis cascade (MCC) reactions for the one-pot synthesis of highly functionalized non-symmetrical malonates. These metal-free reactions are either five-step (olefination/hydrogenation/alkylation/ketenization/esterification) or six-step (olefination/hydrogenation/alkylation/ketenization/esterification/alkylation), and employ aldehydes/ketones, Meldrum's aci...

A facile, moderate to high yielding synthesis of hexahydro-(di)-benzazocinones is described via an intramolecular N-acyliminium ion cyclisation. The iminium ion intermediates are formed from the readily available 4,4-diethoxybutyl amides with an excess of triflic acid. For electron-withdrawing substituents, better yields were obtained from the pre-formed 2-hydroxypyrrolidine amides. From NMR st...

Mechanical point-chirality in a [2]rotaxane is utilized for asymmetric catalysis. Stable enantiomers of the rotaxane result from a bulky group in the middle of the thread preventing a benzylic amide macrocycle shuttling between different sides of a prochiral center, creating point chirality in the vicinity of a secondary amine group. The resulting mechanochirogenesis delivers enantioselective o...