On the Diels–Alder dimerisation of cross-conjugated trienes

Abstract

The first general synthesis of 1-substituted [3]dendralenes has led to the discovery that conjugating groups significantly enhance the rate of Diels-Alder dimerisation relative to both the parent [3]dendralene and to other substituted systems.

Computational and Synthetic Studies with Tetravinylethylenes

“…The short forming bond involving C4 in N-t-22TS leads to stabilization by delocalization of charge through the pentadienyl system derived from [3]dendralene. 24,25 A similar situation might be expected for the preferred TS for the TVE-NMM reaction. In this case, however, a steric factor appears to override this electronic effect.…”

Multicomponent Diene‐Transmissive Diels–Alder Sequences Featuring Aminodendralenes

“…The Si/anti channel is the near exclusive source of Si-based product from 2c,w hereas both Si/anti and Si/syn channels are contributors to the Si-based product in the case of 2b.T he relative free energy data in Table 1i ndicate that p-diastereofacial selectivity in the DA reaction with NMM is stronger for aminodendralene 2c than Them ain structural features of the reactant aminodendralenes,a sd iscussed above,a re essentially retained in the respective Diels-Alder transition structures (TSs), as exemplified by 2c-endo-Re-syn-TS and 2c-endo-Si-anti-TS (Figure 3). [24] Te thering the dienophile to the amine (as in 10 a-c) permits the second cycloaddition (11!12)toberealized in an intramolecular [25] fashion (Scheme 6). Thus,t he forming bond lengths in 2c-endo-Re-syn-TS are 2.896 and 2.083 ( Dr = 0.81 ) and for 2c-endo-Si-anti-TS they are 2.905 and 2.072 ( Dr = 0.83 ).…”

“…These reactions are extraordinarily easy to perform in the laboratory,i nm ost cases involving the mixing of simple precursors.The incorporation of a1-amino-substituent on the [3]dendralene backbone simultaneously augments both its reactivity and selectivity in diene-transmissive Diels-Alder sequences, [24] at the same time delivering highly functionalized multicyclic products akin to alkaloids and medicinal agents.T his study demonstrates the diversity of multicomponent transformations with only one amine group at aspecific position of the simplest possible dendralene structure.E vidently,t he possibilities for step-economic synthesis with aminodendralenes are vast. These reactions are extraordinarily easy to perform in the laboratory,i nm ost cases involving the mixing of simple precursors.The incorporation of a1-amino-substituent on the [3]dendralene backbone simultaneously augments both its reactivity and selectivity in diene-transmissive Diels-Alder sequences, [24] at the same time delivering highly functionalized multicyclic products akin to alkaloids and medicinal agents.T his study demonstrates the diversity of multicomponent transformations with only one amine group at aspecific position of the simplest possible dendralene structure.E vidently,t he possibilities for step-economic synthesis with aminodendralenes are vast.…”

“…This large degree of bond-forming asynchronicity is ageneral characteristic of dendralenes in their DA addition reactions. [24] Te thering the dienophile to the amine (as in 10 a-c) permits the second cycloaddition (11!12)toberealized in an intramolecular [25] fashion (Scheme 6). Theb enefits of employing this tactic include:1)the generation of additional structural complexity with complete orientational regioselectivity,2 )attainment of products with complementary stereoselectivity to the intermolecular process, [26] and 3) the ability to deploy nonactivated dienophiles (10 a).…”

“…In summary,the first multicomponent reaction sequences involving dendralenic intermediates have been devised. These reactions are extraordinarily easy to perform in the laboratory,i nm ost cases involving the mixing of simple precursors.The incorporation of a1-amino-substituent on the [3]dendralene backbone simultaneously augments both its reactivity and selectivity in diene-transmissive Diels-Alder sequences, [24] at the same time delivering highly functionalized multicyclic products akin to alkaloids and medicinal agents.T his study demonstrates the diversity of multicomponent transformations with only one amine group at aspecific position of the simplest possible dendralene structure.E vidently,t he possibilities for step-economic synthesis with aminodendralenes are vast.…”