Merritt B. Andrus

The asymmetric kharasch reaction. Catalytic enantioselective allylic acyloxylation of olefins with chiral copper(I) complexes and tert-butyl perbenzoate

Olefins were treated with tert-butyl perbenzoate in the presence of hiral copper(I) triflate bisoxazoline complexes to give non-racemic allyl benzoates as products. The yields range from 34 to 62% and the enantiomeric excesses from 30 to 81%. A model for the selectivity is proposed.

CATALYTIC ENANTIOSELECTIVE ALLYLIC OXIDATION OF OLEFINS WITH COPPER(I) CATALYSTS AND NEW PERESTER OXIDANTS

Asymmetric allylic oxidation of cyclic olefins using a catalytic amount of copper(I) bisoxazoline complexes and new peresters was investigated to give allylic benzoate esters in high selectivity (∼80%ee), yield (70–80%), and at reasonable rates (5–7 d) at −20 °C in acetonitrile. Cyclohexene reacted with para-chloro tert-butylperbenzoate and 15 mol% diphenylbisoxazoline-copper(I) hexafluorophosphate to give benzoate product in 83% yield and 75% ee.

Synthesis of octalactin lactone and side chain

Abstract Two key intermediates of (+)-octalactin A, a potent new cytotoxic natural product, have been synthesized in a direct, and efficient manner. Lactone 1 was made using a substrate controlled lactonization reaction using the carbodiimide EDCI and two crotylborane additions were used to access the precursor hydroxyacid. The importance of proper substitution in the hydroxyacid tether is noted for successful medium-ring lactonization. Synthesis of the side chain vinyl iodide 2 employed an asymmetric allenylboronate addition.

SELECTIVE DIHYDROXYLATION OF NON-CONJUGATED DIENES IN FAVOR OF THE TERMINAL OLEFIN

Abstract Non-conjugated dienes were dihydroxylated using the commercially available osmium tetroxide AD-mix-α reagent resulting in highly regioselective dihydroxylation of the terminal olefin rather than the internal, more substituted olefin. These findings now allow for the use of allylmetal reagents on substrates where preexisting internal olefins are present. The resultant diol can be cleaved to the aldehyde allowing for subsequent transformations. This selectivity is controled by a steric effect imposed by the allylic silyl ether adjacent to the internal olefin.

Asymmetric additions to dichlorophenyldioxane, a new chiral acetal

Abstract 4-(2,6-Dichlorophenyl)-1,3-dioxanes have been reacted with weak nucleophiles and TiCl 4 to give benzyl ethers with high selectivity. The major products are consistent with an SN 2 -like mechanism. The benzyl ether is removed in one step using Li/NH 3 to give non-racemic secondary alcohols.