Tuning the Stability and the Reactivity of Substituted [3]Dendralenes for Quick Access to Diverse Copiously Functionalized Fused Polycycles with Step and Atom Economy.

This is the first comprehensive study that details the synthesis of stable acyclic trisubstituted [3]dendralenes and deciphers their structural requisite for a successful diene transmissive Diels-Alder (DTDA) reaction by employing two different dienophiles and eventually generating a small repository of complex molecules, thus exemplifying how substituted [3]dendralenes could be deployed in diversity-oriented synthesis with high selectivities. A balance of reactivity and stability was struck by prudent selection of the position and nature of functional groups on these [3]dendralenes. Upon tandem Diels-Alder reactions with several symmetrical as well as unsymmetrical dienophiles, these dendralenes afforded diversity-oriented quick access to many polycyclic complex motifs possessing several functional groups and multiple stereogenic centers. Thus, the full potential of the dendralenes could be harnessed. The reactions proceeded under mild conditions with step and atom economy and were highly regio- and stereoselective besides being excellent yielding. The DTDA sequence resulted in the generation of four new carbon-carbon bonds, two new rings, and 3-7 stereogenic centers. The key feature of the method is that we could rapidly generate complexity along with functional and structural diversity from a trivial acyclic substrate with no stereogenic centers.