Thermal Intramolecular [2+2] Cycloaddition of Allenenes and Allenynes: Diastereoselective Access to Bicyclic Nitrogen Heterocycles

Abstract

Einen Weg zu Bicyclo[4.2.0]octan‐Derivaten bietet die [2+2]‐Cycloaddition von Allenenen oder Alleninen. Die thermische intramolekulare [2+2]‐Cycloaddition einfacher Allene 1 mit einer zusätzlichen Mehrfachbindung führt in guten bis ausgezeichneten Ausbeuten direkt und regioselektiv zu den distalen Addukten 2.

Controllable [2+2] Cycloadditions of 1,5‐Bisallenyl‐Substituted Compounds

“…Reactions of allenenes 1 activated thermally4 and photochemically5 have been reported to afford distal adducts4 2 and proximal adducts5 3 , respectively, as a result of the regioselectivity of the reactions (Scheme 1). [2+2] Cycloadditions of allenynes 4 have been realized by heating,4d or from the catalytic action of transition‐metal complexes 6. However, to the best of our knowledge, reports of [2+2] cycloaddition reactions between two allenes are limited 7.…”

Engaging Yne‐Allenes in Cycloaddition Reactions: Recent Developments

“…One of the most interesting advances in the field of cycloaddition reactions is the involvement of [2 + 2] cycloaddition reactions to the generation of different types of functionalized molecules containing heterocyclic or isocyclic rings, which prove to be the most frequently used strategic tools to access four‐membered cyclic compounds in recent years. [ 51 ] In particular, intramolecular [2 + 2] cycloaddition between an allene unit and an alkene or an alkyne moiety represents a powerful and highly atom‐economic approach to furnish cyclobutanes and cyclobutenes under thermal, [ 52‐54 ] photochemical [ 55‐58 ] and transition metal catalyzed [ 59‐62 ] conditions. In 2016, Shi and co‐workers reported an elegant and highly regioselective [2 + 2] cycloaddition of yne‐allenes 33 for the synthesis of spirosubstituted cyclobutenes 34 in good to excellent yields (Scheme 10).…”

Acid‐Catalyzed Intramolecular [2+2] Cycloaddition of Ene‐allenones: Facile Access to Bicyclo[n.2.0] Frameworks

“…Although the [2+2] cycloadditions of allenyl sulfones by Padwa et al demonstrated that the regioselectivity could be controlled by using different substrates, [7] the sulfonyl group must be removed for further elaboration and the regioselectivity may be inconsistent in complex molecules. [4d] Recently, difluoroallenes, [8] b-lactamtethered allenes, [9] diyne-diallenes, [10] and allenynes [11] have also been employed as substrates to overcome such drawbacks. Unfortunately, many of these reactions involved hightemperature conditions that would limit their use in the synthesis of complex molecules.…”