Table 3.

ΔG^‡ Values in kcal/mol for the Reaction of Benzofurans and -Thiophenes with Substituted Furans

entry	aryne, X	furan, R	ΔG‡ (a)	ΔG‡ (b)
1	27, O	H	9.2
2	28, O	H	9.1
3	29, O	H	7.3
4	27, O	t-Bu	4.9	6.4
5	28, O	t-Bu	5.8	4.9
6	29, O	t-Bu	6.2	a
7	27, S	H	9.6
8	28, S	H	8.9
9	29, S	H	8.4
10	27, S	t-Bu	5.4	6.5
11	28, S	t-Bu	5.5	4.8
12	29, S	t-Bu	5.8	a

^aNo barrier to reaction is predicted in the gas phase or continuum solution.