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DOI: 10.1055/s-0036-1591609
Three-Component Synthesis of Benzopyrans from δ-Acetoxy Allenoates
Construction of Polycyclic Frameworks via a DMAP-Catalyzed Tandem Addition–(4+2) Annulation Sequence of δ-Acetoxy Allenoate.
Org. Biomol. Chem. 2017;
15: 4807-4810
Publication History
Publication Date:
19 October 2017 (online)
Significance
This work derived a complementary approach to that developed in previous work by this group in which DABCO was used as an amine catalyst to afford 4H-chromene-type products (Org. Lett. 2015, 17, 1106). The rapid construction of complex polycyclic ring systems 3a and 3b reported here involves the reaction of a δ-acetoxy allenoate 1 with an oxadiene species 2a or 2b with DMAP as a catalyst.
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Comment
The authors propose that the reaction of 1 with 2a in the presence of DMAP generates intermediate A, which undergoes a [4+2] annulation to form product 3a. Extension of this work to substituted oxadienes led to a range of polycyclic structures, and, interestingly, reaction with 3-(pyrrol-2-yl)acrylonitriles 2b led to 5,5,6-ring-fused products 3b. The utility and applications of these core structures are not disclosed in this report, but further work is underway. Further discussion and, perhaps, computational work might better illustrate the basis for the difference in reactivity between the amine catalysts.
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