2-Picoline efficiently catalyzes the formation of α,β-enones from acetylenedicarboxylates and aldehydes in the presence of alkenes, thereby leading to pyrans in moderate to good yields with complete regioselectivities. This synthetic method of pyrans is represented as a first example of catalytic and direct [2 + 2 + 2] cycloaddition of three different components under the metal-free conditions.
![Graphical abstract: 2-Picoline catalyst-triggered [2 + 2 + 2] cycloaddition-type reaction of acetylenedicarboxylates, aldehydes and alkenes](http://hg.y866.cn/compound/lib/scimg/usr/1/C8OB01774C.jpg)