absolute stereochemistry has been achieved by generating the reactive intermediate (the diazo compound) in situ from tosylhydrazone salts (see scheme, PTC=phase-transfer catalyst, Ts=toluene-4-sulfonyl). High yields (58-82 %), high d.r. (88:12-98:2), and high ee values (87-94 %) have been obtained using a new class of stable chiral sulfides at low catalyst loading (5 mol %) and [Rh2 (OAc)4 ] (0.5 mol %).
Practical and Highly Selective Sulfur Ylide Mediated Asymmetric Epoxidations and Aziridinations Using an Inexpensive, Readily Available Chiral Sulfide. Applications to the Synthesis of Quinine and Quinidine
作者:Ona Illa、Muhammad Arshad、Abel Ros、Eoghan M. McGarrigle、Varinder K. Aggarwal
DOI:10.1021/ja9100276
日期:2010.2.17
one-step synthesis of a chiral sulfide which exhibits outstanding selectivities in sulfur ylide mediated asymmetric epoxidations and aziridinations. In particular reactions of benzyl and allylic sulfonium salts with both aromatic and aliphatic aldehydes gave epoxides with perfect enantioselectivities and the highest diastereoselectivities reported to date. In addition reactions with imines gave aziridines
Marked effect of a catalytic amount of an amine on selective epoxidation of aliphatic and aromatic olefins witht-butyl hydroperoxide and a molybdenum oxide chelate
In the presence of a catalyticamount of an appropriate amine, epoxides were selectively obtained in good yields from reaction of aliphatic and aromatic olefins witht-butyl hydroperoxide and MoO2(acac)2 in carbon tetrachloride.
A new chrial organosulfide was synthesized through an unexpected Wagner–Meerwein rearrangement. This organosulfide could catalyze the epoxidation reaction of various aromatic aldehydes smoothly with benzyl bromide to give trans-diaryl epoxides in satisfactory yields (60–84%) with excellent diastereoselectivities (trans:cis=95:5–100:0) and good to excellent enantioselectivities (86–96% ee).