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. Author manuscript; available in PMC: 2021 Feb 5.
Published in final edited form as: J Am Chem Soc. 2020 Jan 17;142(5):2187–2192. doi: 10.1021/jacs.9b12319

Table 1.

Effect of Additives and Temperature on Cyclization Diastereoselectivity

graphic file with name nihms-1578260-t0005.jpg
entry additive temp (°C) d.r. (6:19) yield (%)a
1 AcCl −78 87:13 68%
2 AcCl 20 60:40 n.d.
3 Ac2O −78 –b –b
4 BF3·Et2O −78 84:16 72
5 TMSCl −78 95:5 78
6 HCl −78 95:5 70
7c TMSCl 40 27:73 69
8d,e TMSCl 40 27:73 n.d.
9 HCl 40 66:34 n.d.
a

Isolated yield over 2 steps starting from 7

b

no reaction

c

reaction time of 2 days

d

starting material was pure 6

e

reaction time 4 days.

n.d. = not determined.