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. 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 6.

Double in situ Generation of Ketenes.a graphic file with name nihms-813507-t0010.jpg

entry catalyst (mol%) R1 R2 R3 % yieldb % eec Z:E d 3
1 MeQd (10) Me Me Ph 61 91 >97:3 (−)e-3a
2 MeQd (2.5) Me Me Ph 74 92 99:1 (−)e-3a
3 TMSQ (10) Me Me Ph 67 93 99:1 (+)e-3a
4 MeQd (10) Me Et Ph 48 95 78:22 (−)-3b
5 MeQd (10) Et Me Ph 71 97 98:2 (−)-3e
6 MeQd (10) Et Et Ph 35 97 86:14 (−)-3f
7 MeQd (10)f Me Ph Et 41 >99 33:67 E-(−)-3p
a

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

b

Isolated yield for both isomers.

c

ee determined by chiral HPLC.

d

Z:E ratio determined by GC-MS analysis.

e

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

f

Reaction conducted in the presence of 2 equiv LiClO4.