Insertion Of Benzynes Into Carbon-carbon And Carbon-nitrogen Double Bonds

As a highly reactive organic intermediates, benzyne has become an emerging field of organicsynthesis research in recent years. The strong electrophilic property makes it possible to insert into some C=X bonds, then form a benzannulated four-membered rings. The strain of these rings allow for a ready,spontaneous opening to afford orth-quinomethide analogues (oQMs). Subsequent nucleophilic additionre-aromatizes the intermediates to achieve orth-difunctionalization of benzyne. This non-traditionalapproach enable direct introduction of functional groups into adjacent positions of the aromatic group,which adds new cases for organic synthesis.Benzyne reacts with electronically biased vinylogous amides in a [2+2] cycloaddition/ring-openingfashion to furnish an oQDM intermediate. This oQDM intermediate was trapped by a nucleophile (alcohol)completing a C=C double bond insertion to achieve orth-difunctionalization of benzyne. We find that apropiolate-amine (catalytic amount)-benzyne “one-pot” system can also form the same final product.Benzyne reacts with carbodiimide (which have a special accumulated double) in a [2+2]cycloaddition/ring-opening fashion to furnish an oQM intermediate. This oQM intermediate was trappedby a nucleophile (H2O or alcohol) completing a C=N double bond insertion to achieve amide, amidineand imidate compounds.These insertion reactions furnish unstable orth-quinomethide–typed intermediates, which areconfirmed favorable over inner-salt structures by computational studies. This study provides a new way ofthinking for insertion reaction mechanism research.