[3]‐1‐Azadendralenes as Versatile Building Blocks for the Stereoselective Synthesis of Polysubstituted Hexahydroquinazolin‐2‐ones and Hexahydrobenzothiazine‐2‐­imines

Abstract

International audienceA 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 orde

Diels-Alder reactions of 1-amino-1,3-dienes and related systems

“…The diene-transmissive hetero-DA reaction of azatrienes 563, prepared from 2-vinyl α,βunsaturated aldehydes 562, with tosyl isocyanate afforded alkenyl tetrahydropyridines 544 (Scheme 137) [337,338]. The second DA reaction with the same previously mentioned dienophiles gave diastereoselectively hexahydroquinazolin-2(1H)-ones 565-567.…”

“…In the case of methyl vinyl ketone the DA reaction was performed using TMSOTf (20 mol%) as catalyst. The reaction of azatrienes 563 with aryl isothiocyanates allowed the synthesis of hexahydrobenzothiazine-2-imines [338].…”

Oxadendralenes in asymmetric organocatalysis for the construction of tetrahydroisochromenes

“…1 , top), despite the ability of heterodendralenes to facilitate hetero-Diels–Alder reactions yielding unprecedented polycyclic frameworks with exceptional atom economy. 8 …”