A phosphine-catalyzed tandem cyclization reaction has been developed to provide a series of chromeno [4,3-b]pyrrole derivatives, which contain three consecutive asymmetric centers. The reaction has a good yield, excellent stereoselectivity, and Z/E selectivity. The new method is simple, requires only mild conditions, and shows tolerance for various functional groups. Similarly, this reaction can be catalyzed by a chiral phosphine catalyst to achieve asymmetric synthesis. cascade cycloaddition strategy for facily synthesizing chromenopyrrole derivatives from aldimine esters and δ-acetoxy allenoates. In particular, a wide range of products have been afforded in generally good yields with excellent diastereoselectivities. In addition, by using a chiral phosphine catalyst, the cycloaddition reaction can also initially realize the asymmetric synthesis of chromeno [4,3-b]pyrrole. This protocol can be expected to find wide synthetic application because of its simple operation, mild reaction conditions, high efficiency, and high chemo-and enantioselectivity.

A catalyst-free [3 + 2] cycloaddition reaction of electron-deficient alkynes and o -hydroxyaryl azomethine ylides in water was developed, affording pyrroline derivatives in moderate to high yields (up to 90%).

Text. A general method for the synthesis of structural diversity and complexity of azepines from aldimine esters and β'-acetoxy allenoates is reported. Under phosphine catalysis, a [4 + 3] cycloaddition for the formation of 1,3-dihydro-2H-azepine-2,2,4-tricarboxylates was achieved with broad substrate scope under mild reactions. A switchable process was given and a variety of important 2,3-dihydrochromeno[4,3-b] azepin-6(1H)-ones were selectively formed when the reaction was performed in the presence of Cs 2 CO 3 and PPh 3 , which involved an intramolecular ester group migration and subsequent lactonization of 1,3-dihydro-2Hazepine-2,2,4-tricarboxylates. Besides easy handle process, high synthetic value of resulting products, it is worth to note that this work showed the novel example of 1,5-ethoxycarbonyl migration.

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