Synthesis of Polyfunctionalized 4H-Pyrans

Table 3

Synthesis of substituted pyrans from acetylacetone via Scheme 1.^a,b

Entry	R	Product	Time (h)	% Yield^c	m.p. (°C)
1	3-NO2C6H4	1a	3	85	161- 162 [17]
2	4-NO2C6H4	1b	3.0	82	168-169
3	4-ClC6H4	1c	3.5	88	130-131
4	Ph	1d	5	72	293– 195 [17]
5	3-OHC6H4	1e	3	82	158-159
6	4-MeOC6H4	1f	6	78	210– 213 [17]
7	4-CH3C6H4	1g	6	81	274– 276 [17]
8	3-Pyridyl	1h	3	87	163-164
9	2-Furfuryl	1i	3.5	90	166-167

^aAll reactions were carried out at room temperature; ^bequimolar ratio of all the reactants with 30 mg Amberlyst A21/mmol of aldehyde; ^cisolated yields.