Stereospecific Hydrogenolysis of Lactones: Application to the Total Syntheses of (R)-ar-Himachalene and (R)-Curcumene

Abstract

A straightforward strategy for the syntheses of curcumene and ar-himachalene is reported. Synthetic highlights include a catalytic and asymmetric vinylogous Mukaiyama reaction and a stereospecific hydrogenolysis of a tertiary benzylic center using Pd/C or Ni/Raney catalysts. Notably, using Ni/Raney, the stereoselectivity outcome (inversion vs retention) of the hydrogenolysis depends on the tertiary benzylic alcohol substitution.

Very short highly enantioselective Grignard synthesis of 2,2-disubstituted tetrahydrofurans and tetrahydropyrans

“…It seems that para -substitution on the phenyl ring (at least with methyl) does not change the face-selectivity on the phenone. This 3-step synthesis of lactone 12 marks a notable improvement compared to other strategies reported so far, the shortest of which were both 5-steps 12b,26…”

Atropselective Synthesis of N,C-Bis(diphenylphosphanes) from Bridged 2-Arylindoles Based on Effective Point-to-Axial Asymmetric Inductions after an Unusual Dilithiation

“…Less Pd/C, other catalysts [Pd-black, Pd­(OH) 2 ], or other solvents (MeOH, AcOEt, and 2-Me-THF) gave inferior selectivities. Hydrogenolyses of tertiary C benzylic –O bonds akin to our examples 29 → 30 and dia - 29 → dia - 30 and proceeding with inversions of configurations, too, were first investigated by Mitsui et al One such hydrogenolysis of a tolyl-substituted δ-lactone was accomplished by Campagne et al during our own studies.…”

The chemistry of the himachalenes and atlantones from Cedrus

“…Campagne et al 77 have reported a straightforward strategy for the syntheses (R) ar-himachalene. Synthesis includes a catalytic and asymmetric vinylogous Mukaiyama reaction and a stereospecific hydrogenolysis of a tertiary benzylic center using Pd/C or Ni/Raney catalysts (Scheme 19).…”