Substrate scope of the synthesis of 2,4-dimethoxy-THPQs 4(a–d)^a.

Entries	R	Product	Time (min)	% Yieldb
1	4-Cl	4a	90	73
2	4-H	4b	90	71
3	3-OMe	4c	90	72
4	3-Cl	4d	90	68

^aReaction condition: 1 mmol aldehyde 1(a–d), 1 mmol dimedone 2 and 1 mmol 6-amino-2,4-dimethoxypyrimidine 3.

^bIsolated yield.