Table 2.

Optimization of Ullmann-Type C-N Coupling and Radiofluorination of ¹⁸F-2 ^a

Entry	Compd 6 (eq.)^b	Base(s) (eq.)^b	CuI (eq.)^b	Yields^c
1	1	Cs₂CO₃/KOBu^t(3/3)	0.5	10%
2	3	Cs₂CO₃/KOBu^t(3/3)	0.5	45%
3	3	Cs₂CO₃/KOBu^t(3/5)	0.5	15%
4	3	Cs₂CO₃ only (3)	0.5	trace
5	3	KOBu^t only (3)	0.5	15%
6	0.2	Cs₂CO₃/KOBu^t(3/3)	0.5	10%
7	0.2	Cs₂CO₃/KOBu^t	1	22%
		(1.2/1.2)
8^d	¹⁸F-6	Cs₂CO₃/KOBu^t	1	10%^e
		(1.2/1.2)

Unless otherwise noted, all reactions were carried out as follows: To a dried flask with trifluoroacetate salt 7 (7.1 mg), an appropriate amount of Cs₂CO₃ and tert-butoxide was added acetonitrile (0.5 mL). The resulting solution was allowed to react at room temperature for 5-10 min, then unlabeled compound 6 and CuI were added, and the resulting mixture was heated at 115-118 °C for 90 min.

eq. = equivalents relative to the trifluoroacetate salt 7.

Yield of isolated pure product.

¹⁸F-6 was used and the ratio to 7 was not calculated.

Yield of pure product ¹⁸F-2 isolated by semi-preparative HPLC.