Skip to main content
. Author manuscript; available in PMC: 2017 Sep 2.
Published in final edited form as: J Org Chem. 2016 Aug 12;81(17):7824–7837. doi: 10.1021/acs.joc.6b01481

Table 5.

Asymmetric Synthesis of E-Ketene Heterodimers.a graphic file with name nihms-813507-t0009.jpg

entry (+)/(−)-3b catalyst R1 R2 R3 % yield % eec Z:E d
1 (+)-3p TMSQ Me Et Ph 56 85 16:84
2 (−)-3p MeQd Me Et Ph 57 94 13:87
3e (+)-3q TMSQ Me n-Bu Ph 69 84 24:76
4e (−)-3q MeQd Me n-Bu Ph 78 92 26:74
5 (+)-3r TMSQ Me i-Bu Ph 78 96 4:96
6 (−)-3r MeQd Me i-Bu Ph 83 98 3:97
7 (+)-3s TMSQ Et Et Ph 86 93 26:74
8 (−)-3s MeQd Et Et Ph 86 88 24:76
9e (−)-3t TMSQ Et i-Bu Ph 76 97 6:94
10e (+)-3t MeQd Et i-Bu Ph 88 98 5:95
a

Only one heterodimer regioisomer observed in all cases by GC-MS analysis of crudes and NMR analysis of 3.

b

Sign of specific rotation; (+)-enantiomer or (−)-enantiomer.

c

ee determined by chiral HPLC.

d

Z:E ratio determined by GC-MS analysis of crudes and confirmed by 1H NMR analysis.

e

In these cases 1 equiv of LiClO4 was used as an additive.