A general method for the selective hydrogenation of alkenyl halides to alkyl halides is described. Fluoro, chloro, bromo, iodo, and gem-dihaloalkenes are viable substrates for the transformation. The selectivity of the hydrogenation is consistent with reduction by a hydrogen atom transfer pathway.
Maximized divergence: The hasubanan alkaloids given in the scheme have been synthesized in eight or nine steps from the aryl azide 1. The utility of 5‐trimethylsilylcyclopentadiene as an easily removed, stabilizing stereocontrol element has been demonstrated.
One route fits all: Syntheses of the title complex tetracyclic alkaloids are described. The routes feature the strategic application of 5‐trimethylsilylcyclopentadiene, a selective hydrostannylation of a complex enyne, a Hosomi–Sakurai cyclization to form the skeleton of the targets, an allylic formate rearrangement to construct the spirocyclopentenone rings, and a selective hydrogenation to establish the alkyl chloride functional group of (−)‐acutumine.
A general method
for the N-arylation of amino
acid esters with aryl triflates is described. Both α- and β-amino
acid esters, including methyl, tert-butyl, and benzyl
esters, are viable substrates. Reaction optimization was carried out
by design of experiment (DOE) analysis using JMP software. The mild
reaction conditions, which use t-BuBrettPhos Pd G3
or G4 precatalyst, result in minimal racemization of the amino acid
ester. This method is the first synthetic application of the t-BuBrettPhos Pd G4 precatalyst. Mechanistic studies show
that the observed erosion in enantiomeric excess is due to racemization
of the amino acid ester starting material and not of the product.
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