All for one: Phosphine‐ligated platinum(II) electrophiles can activate polyalkenes for cyclase enzyme mimicking cascade cyclizations without the need for special terminating groups (see scheme). Like the cyclase enzymes, terminal alkenes that generate tertiary cations are good substrates, although the details of the cation termination depend on the alkene arrangement.

Stereocontrolled Mn-mediated addition of alkyl iodides to chiral N-acylhydrazones enables strategic C−C bond constructions at the stereogenic centers of chiral amines. Applying this strategy to quinine suggested complementary synthetic approaches to construct C−C bonds attached at the nitrogenbearing stereogenic center using multifunctional alkyl iodides 6a− d as radical precursors, or using multifunctional chiral Nacylhydrazones 26a−d as radical acceptors. These were included among Mn-mediated radical additions of various alkyl iodides to a range of chiral N-acylhydrazone radical acceptors, leading to the discovery that pyridine and alkene functionalities are incompatible. In a revised strategy, these functionalities are avoided during the Mn-mediated radical addition of 6d to chiral Nacylhydrazone 22b, which generated a key C−C bond with complete stereochemical control at the chiral amine carbon of quinine. Subsequent elaboration included two sequential cyclizations to complete the azabicyclo[2.2.2]octane ring system. Group selectivity between two 2-iodoethyl groups during the second cyclization favored an undesired azabicyclo[3.2.1]octane ring system, an outcome that was found to be consistent with transition state calculations at the B3LYP/6-31G(d) level. Group differentiation at an earlier stage enabled an alternative regioconvergent pathway; this furnished the desired azabicyclo[2.2.2]octane ring system and afforded quincorine (21b), completing a formal synthesis of quinine.

A radical-ionic annulation approach to functionalized perhydroisoquinolines involving Mn-mediated coupling of alkyl iodides and chiral N-acylhydrazones was achieved using only 1.25 equiv of the alkyl iodide. Application of this reaction to alkene-containing substrates en route to quinine offered modest yields, decreasing on scaleup. Control experiments revealed that the alkene interfered with the coupling reaction. A revised approach involving prior oxidation of the alkene offered 93% yield in the Mn-mediated coupling, with the adduct obtained as a single diastereomer.

[reaction: see text] Chiral N-acylhydrazones derived from commercially available 4-benzyl-2-oxazolidinone provide a rigid, conformationally restricted template to impart facial selectivity in additions to C=N bonds. In the presence of indium(III) trifluoromethanesulfonate [In(OTf)3], N-acylhydrazones undergo highly diastereoselective fluoride-initiated additions of allylsilanes (aza-Sakurai reaction). Mechanistic studies including control experiments and comparisons with allyltributylstannane, allylmagnesium bromide, and allylindium species implicate a dual activation mechanism involving addition of an allylfluorosilicate species to a chelate formed from In(OTf)3 and the chiral N-acylhydrazone. The N-N bonds of the adducts are readily cleaved in a two-step protocol to provide synthetically useful homoallylic N-trifluoroacetamides. Further elaboration of the latter compounds through Wacker oxidation and olefin metathesis provides diversely functionalized building blocks and expands the potential applications of this C-C bond construction approach to asymmetric amine synthesis.