Vinylation of cyclohexanone enolates using vinyl ether-iron complexes. Diastereoselectivity of carbon-carbon bond formation

Identification of the Optimal Framework for Nitroxyl Radical/Hydroxylamine in Copper-Cocatalyzed Aerobic Alcohol Oxidation

8-Azabicyclo[3.2.1]octan-8-ol (ABOOL) and 7-azabicyclo[2.2.1]heptan-7-ol (ABHOL) are the main homologues of hydroxylamine 2-azaadamantan-2-ol (AZADOL) and 9-azabicyclo[3.3.1]nonan-9-ol. Both homologues feature a small bicyclic backbone and are known to be stable; however, to date, they have not been used as catalysts for alcohol oxidation. Herein, we report that these hydroxylamines can efficiently catalyze the oxidation of various secondary alcohols to their corresponding ketones using molecular oxygen in ambient air as the terminal oxidant and copper cocatalysts at room temperature. Furthermore, we show that ABOOL and ABHOL can be easily synthesized from commercially available materials.

Chemoenzymatic Synthesis of the Intermediates in the Peppermint Monoterpenoid Biosynthetic Pathway

A chemoenzymatic approach providing access to all four intermediates in the peppermint biosynthetic pathway between limonene and menthone/isomenthone, including noncommercially available intermediates (-)- trans-isopiperitenol (2), (-)-isopiperitenone (3), and (+)- cis-isopulegone (4), is described. Oxidation of (+)-isopulegol (13) followed by enolate selenation and oxidative elimination steps provides (-)-isopiperitenone (3). A chemical reduction and separation route from (3) provides both native (-)- trans-isopiperitenol (2) and isomer (-)- cis-isopiperitenol (18), while enzymatic conjugate reduction of (-)-isopiperitenone (3) with IPR [(-)-isopiperitenone reductase)] provides (+)- cis-isopulegone (4). This undergoes facile base-mediated chemical epimerization to (+)-pulegone (5), which is subsequently shown to be a substrate for NtDBR ( Nicotiana tabacum double-bond reductase) to afford (-)-menthone (7) and (+)-isomenthone (8).

Enolate Additions to a Chiral 3-Hydroxypropionate 2,3-Dication Equivalent. Enantioselective Synthesis of beta,delta-Dihydroxy Esters

The use of optically active dicarbonyl cyclopentadienyliron(vinyl ether) BF(4) salts, 3 and 4, as enantioselective 3-hydroxypropionate 2,3-dication equivalents is outlined. Complexes 3 and 4 are readily available by exchange etherification of 2, and these have been transformed to enantiomeric dicarbonyl (eta-cyclopentadienyliron)(eta(2)-1-methoxypropene) BF(4) 5 and ent-5. Complex 5 has been converted to the corresponding p-methoxybenzyloxy vinyl ether complex 7 by exchange etherification. Condensation of this salt with a number of terminal and nonterminal enolates yields adducts, which are then transformed by redox-promoted alkoxycarbonylation, followed by alcohol deprotection, to optically active 2-methyl-3-hydroxy-5 keto esters. 1,3-Reduction of these ketols can be effected to give either syn- or anti-1,3-diols and thence their related pentanolides.