Table 1.

Dependence of β‐selectivity with decreasing temperature.

No.	Donor	Temp [°C]	Time	Yield [%]	α/β ratio
1	18	40	2 h	82	1:2
2	18	0	5 h	76	1:5
3	18	−60	3 days	76	1:29
4	19	40	5 min	83	1:4
5	19	0	30 min	74	1:9
6	19	−60	12 h	73	1:50