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.
An iodine‐promoted regioselective sulfenylation/deoxygenation/aromatization reaction of 1‐tetralones with disulfides has been developed. This process could be modified to synthesize 2‐naphthyl thioethers and 1‐naphthyl thioethers in moderate to excellent yields, respectively. Furthermore, when the reaction was extended to 2‐tetralones, 2‐naphthyl thioethers were obtained as the sole products. The current study bridges the deoxygenation and sulfenylation/aromatization of ketones, thus providing a new tool in organic synthesis.magnified image
A convenient [3 + 2] annulation of azomethine ylides with allenoates promoted by triethylamine produced highly functionalized 2,5-dihydropyrrole derivatives in moderate to excellent yields under mild conditions. The potential utility of this reaction indicates that this reaction could be performed on the gram scale and the synthesized functionalized 2,5-dihydropyrrole derivatives could be further transformed into other interesting heterocycles. The mechanism for the transformation is a tandem β-addition/Mannich cyclization process.
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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