[3]‐1‐Azadendralenes as Versatile Building Blocks for the Stereoselective Synthesis of Polysubstituted Hexahydroquinazolin‐2‐ones and Hexahydrobenzothiazine‐2‐imines
Abstract
The diene‐transmissive hetero Diels–Alder reaction of cross‐conjugated 1‐azatrienes was developed to produce stereoselectively ring‐fused nitrogen heterocycles. [4+2] cycloaddition reaction with tosyl isocyanate or aryl isothiocyanates gave regioselectively monocycloadducts that reacted with dienophiles. Skeletal diversity is achieved by the addition sequence of the three reaction partners.
Abstract
A diene‐transmissive hetero‐Diels–Alder reaction of cross‐conjugated 1‐azatrienes (3‐1‐azadendralenes) is described for the synthesis of hexahydroquinazolin‐2‐ones and hexahydrobenzothiazine‐2‐imines derivatives. [4+2] Cycloaddition reactions with tosyl isocyanate or aryl isothiocyanates gave mono‐cycloadducts with high chemo‐ and regioselectivities. The second Diels–Alder reaction with representative dienophiles, tetracyanoethylene, N‐phenylmaleimide, and methyl vinyl ketone, stereoselectively produced ring‐fused nitrogen heterocycles. Skeletal diversity can be accessed by combining the three reaction partners – primary amine, tosyl isocyanate, and cross‐conjugated 1‐oxatriene – in a different sequential order.
