Table 2.

One pot synthesis of pyridines from α,β-unsaturated imines and alkynes

Entry	Imine	Alkyne	Time (h)	DHP	% Yielda (isolated)	[O] Temp. (°C)	[O] Time (h)	Pyridine	Overall Yieldb
1			2		98 (97)	0	8		80%
2			2		94 (99)	0	8		69%
3			10		50	23	12		54%
4			4		81	23	12		66%
5			2		98	0	8		54%
6			6		88	23	8		61%
7			4		96	23	14		86%
8			4		98	23	14		69%
9			2		99 (78)	75	16		75%
10			2		99	0	16		73%
11			6		81	75	16		59%
12			8		86	75	16		50%
13			24		76 (70)	120	16		53%c
14			2		74	75	12		64%d
15			2		99	120	16		32%

^aDetermined by NMR integration relative to 2,6-dimethoxytoluene as an internal standard.

^bIsolated overall yields based on starting α,β-unsaturated imine.

^cFor this specific substrate, purified DHP was used for pyridine synthesis and the yield provided is the overall yield for the three steps.

^dThe minor regioisomer with the Ph-substituent in the 2-position was isolated in 26% yield.