Synthesis of Novel D‐Secoestrone Isoquinuclidines by an Unpredicted Iminium Ion‐Induced 1,5‐Hydride Shift

Abstract

Unique 9,13-bridged D-secoestrone alkaloids have been synthesized and structurally characterized. Treatment of 3-methoxy-16,17-secoestra-1,3,5(10)-trien-17-al (6a) with aniline (7) or substituted aniline derivatives 8−28 in the presence of different Lewis and Brønsted acids produces the bridged azaestrone derivatives 51−67 and the alkenes 68−73 in high yields in a domino-type process. The imines 29−50 are proposed as intermediates, undergoing 1,5-hydride shifts via the

Exploration of Forbidden Povarov Processes as a Source of Unexpected Reactivity: A Multicomponent Mannich–Ritter Transformation

“…[12] The quinolone derivative [19] may arise from a complex sequence involving a Grob-type fragmentation, [20] an aza-Michael process, and a 1,6-hydride shift [21] with concomitant elimination of a formaldehyde equivalent. [12] The quinolone derivative [19] may arise from a complex sequence involving a Grob-type fragmentation, [20] an aza-Michael process, and a 1,6-hydride shift [21] with concomitant elimination of a formaldehyde equivalent.…”

Exploration of Forbidden Povarov Processes as a Source of Unexpected Reactivity: A Multicomponent Mannich–Ritter Transformation

“…Chemie unequivocally identified by X-ray structure analysis. [12] The quinolone derivative [19] may arise from a complex sequence involving a Grob-type fragmentation, [20] an aza-Michael process, and a 1,6-hydride shift [21] with concomitant elimination of a formaldehyde equivalent. The fluoropyridine 7 was produced in an analogous manner.…”

CH Bond Functionalization through Intramolecular Hydride Transfer

“…(15)]. 59a,b Exposure of imine 120 to BF 3 ⋅OEt 2 in dichloromethane solution led to the unexpected formation of polycyclic amine 121 in high yield. The simultaneous reduction of the imine and replacement of a benzylic CH bond for a CN bond was rationalized with a 1,5‐hydride shift/ring‐closure sequence with a stabilized benzyl cation intermediate.…”