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. Author manuscript; available in PMC: 2013 Sep 21.
Published in final edited form as: J Org Chem. 2012 Sep 4;77(18):7932–7944. doi: 10.1021/jo301064u

Table 6.

AZ Reaction of Pre-formed Imine 1a' with Added Bases.a

graphic file with name nihms405462u5.jpg
entry pKa baseb base x mol% % yield 5a'c,d % ee 5a'e cis/transc % yield 18a' + 19a'c unreacted 1a' (%)c
1 – none 0 83 (85) 90 100:1 10 <1
2 10.75 Et3N 10 71 (77) 86 25:1 9 6
3 20 <1 – – – 89
4 40 <1 – – – 92
5 10.60 Ph2CHNH2 10 77 (80) 89 27:1 10 <1
6 20 10 _ 12:1 2 86
7 9.20 DMAP 10 <1 _ – – 96
8 20 <1 – – – 80
9 4.60 C6H5NH2 10 73 (78) 88 33:1 8 5
10 20 17 (20) 86 23:1 6 68
a

Unless otherwise specified, the boroxinate catalyst 9 was prepared in CHCl3 from 10 mol% (S)-VAPOL, 30 mol% B(OPh)3 and x mol% of a base to induce boroxinate formation. After 1h at 25 °C, 100 mol% of imine 1a' and 120 mol% EDA 2 were added to the catalyst and the aziridination reaction carried out with 1.0 mmol of imine (0.5 M) for 24 h at 25 °C.

b

All bases were purified by distillation or sublimation.

c

Determined from the 1H NMR spectrum of the crude reaction mixture with Ph3CH as internal standard.

d

Yields in parentheses are after isolation by silica gel chromatography.

e

Determined on purified 5a' by chiral HPLC.