Table 3. Base Screening in the Guanylation of 1a Using HATU in ACN.

entry	base	pKBH in ACNa	yield of 2a (%)
1	triethylamine	18.83	77
2	N,N-diisopropylethylamine	18.60	64
3	N,N-diisopropylamine	18.81	52
4	2,2,6,6-tetramethylpiperidine	18.64	44
5	1,2,2,6,6-pentamethylpiperidine	18.62	54
6	pyridine	12.53	17
7	2,6-lutidine	14.16	11
8	2,6-di(tBu)pyridine	8.05	0
9	4-(N,N-dimethylamino)pyridine	17.95	47
10	4-methoxy-N,N-dimethylaniline	12.72	0

^aRefs.^35–40