Table 1.

Preliminary reaction optimization^a

Entry	[1] mM	[2] mM	[DBU] mM	time/min	temp/°C	%yieldb
1	100	100	100	5.0	75	60
2	"	"	"	5.0	100	69
3	"	"	"	7.5	75	81
4	"	"	"	7.5	100	83
5	"	"	"	10	25	17
6	"	"	"	10	75	85
7	"	"	"	10	100	75
8	"	"	"	12	75	83
9	"	"	"	12	100	81
10	10	100	100	10	75	73
11	100	10	100	10	75	51
12	100	100	10	10	75	10
13	100	100	0	10	75	7

^[a]Reactions (300 μL DMF) were performed in a sealed vessel under a He atmosphere. No carrier added ¹¹CO₂ was trapped from a stream of He gas.

^[b]See supporting information for details related to radiochemical yield calculation.