Optimization of reaction conditions^a.

Entry	Reaction conditions (reagent (equiv))	% Yield of 3ab	% Yield of 2ab
1	K2S (6), 120 °C	51	19
2	K2S (6), 140 °C	66	16
3	K2S (4), 140 °C	42	44
4	K2S (2), 140 °C	10	64
5c	K2S (6), H2O (30), 140 °C	60	19
6	Na2S·9H2O (6), 140 °C	20	15
7	S8 (6), 140 °C	10	71
8	S8 (6), Et3N (10), 140 °C	Trace	98
9d	K2S (6), 140 °C	83	16

^aReactions were run in 0.03 mmol scale for 24 h in Ar (R = hexylheptyl).

^bIsolated yields of 2a and 3a.

^c40 h.

^dBefore heating at 140 °C, the reaction mixture was stirred at 25 °C for 10 min.