Synthesis of 1,2-diols
A catalytic enantio- and diastereoselective addition of alkyl 1,1-diboron reagents to aryl and vinyl aldehydes provides 1,2-hydroxyboronates promoted by a readily available chiral monodentate phosphoramidite-copper complex. Products contain two contiguous stereogenic centers and are obtained in good yield, good d.r., and high e.r. The 1,2-hydroxyboronate products can be transformed into versatile derivatives.
M. V. Joannou, B. S. Moyer, S. J. Meek, J. Am. Chem. Soc., 2015, 137, 6176-6179.
A one-pot, selective cross pinacol-type coupling between two structurally similar aromatic aldehydes in the presence of low-valent titanium gave unsymmetrical pinacols in good yields and diastereoselectivities. This synthetic methodology, which is based on the affinity of the substituents to the surface of titanium, significantly extends the scope of the cross pinacol-type couplings.
X.-F. Duan, J.-X. Feng, G.-F. Zi, Z.-B. Zhang, Synthesis, 2009, 277-282.
A tandem Wittig Rearrangement/aldol reaction of O-benzyl or O-allyl glycolate esters generates two carbon-carbon bonds and two contiguous stereocenters with excellent diastereoselectivity in a single step from simple starting materials. The [1,2]-Wittig rearrangement proceeds under very mild reaction conditions.
M. B. Betrand, J. P. Wolfe, Org. Lett., 2006, 8, 4661-4663.