- Highly diastereoselective addition of cyanide to β-hydroxyketones
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The addition of cyanide with KCN/ZnI2/TMSCN to β-hydroxyketones (R1-CHOH-CO-R2, R1 = i-Pr, R2 = Me, Et, i-Bu, i-Pr, t-Bu, R1 = Et, R2 = t-Bu and R1 = Bn, Ph, R2 = i-Bu) produced syn β-hydroxycyanohydrins in 95% d.e.
- Brunet,Singh Batra,Aguilar,Garcia Ruano
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- On the diastereoselectivity of cyanide addition to β-hydroxyketones: One-pot synthesis of syn β-hydroxycyanohydrins and anti 2,4-dihydroxyamides
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The intrinsic stereoselectivity of the cyanide addition to β-hydroxyketones in the presence of 18-crown-6 or ZnI2 is lower than that previously reported. However, the reaction bears a practical value in that syn β-hydroxycyanohydrins and anti 2,4-dihydroxyamides can be diastereoselectively obtained in reasonable yields in a one-pot procedure. The high d.e.'s initially reported were due to the work-up procedure, where the HCl converted much faster the anti β-hydroxycyanohydrin than the syn product into the corresponding amide. This faster conversion is explained in terms of antichimeric assistance of β-hydroxyl group. Details are given as to the configurational assignment of products by 2D NMR and molecular mechanisms.
- Batra, Manohar Singh,Aguilar, Francisco J.,Brunet, Ernesto
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p. 8169 - 8184
(2007/10/02)
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