Asymmetric Organocatalyzed Oxa‐Michael Cyclizations Derivatization of N‐Boc glycine affords enantioenriched 2‐morpholine ethanol: Br 1. Boc
NaH N H
CO2Et
2. LiBH4, THF, MeOH
OH N Boc
2nd gen HoveydaGrubbs catalyst CH2Cl2
CHO
CHO OH N Boc
1. N H
Ar Ar (20 mol%) OSiMe3
PhCO2H (20 mol%) toluene, -25 oC, 2h
O N Boc
OH
76% ee
2. NaBH4, MeOH
Use of the Boc protecting group is essential to substrate synthesis.
Synthesis and X‐ray diffraction of a camphanoyl derivative of 2H‐pyran‐2‐ylethanol reveals absolute configuration of oxa‐Michael cyclization products:
Observed absolute stereochemistry is consistent with a stereochemical model in which the bulky catalyst substituent controls configuration at the newly‐formed stereogenic center.
