Divergent Asymmetric Synthesis of Polycyclic Compounds via Vinyl Triazenes

Abstract

Vinyl triazenes were obtained by enantioselective [2+2] cycloaddition reactions of bicyclic alkenes with 1-alkynyl triazenes in the presence of a Ru catalyst with a chiral cyclopentadienyl ligand. These triazenes serve as unique vinyl cation surrogates. Under acidic conditions, the triazene functionality can be replaced with a variety of groups, including halides, alkoxides, sulfoxides, amides, arenes, and heteroarenes, thus providing efficient access to a pool of chiral polycyclic compounds.

Divergent Asymmetric Synthesis of Polycyclic Compounds via Vinyl Triazenes

“…X-ray crystallographic analysis of 3ca allowed the unambiguous determination of its absolute configuration. [11] Thediester-substituted alkene 1b gave cyclobutene 3ba in 84 %y ield with e.r. 94.…”

“…Thei nterception of the intermediate was demonstrated with methanol and pentanethiol, which delivered enol ether 13 and vinyl sulfide 11.W ith water as the nucleophile, cyclobutanone 14 was obtained as as ingle diastereomer. [11] When the protonation was carried out in wet acetonitrile, ac lean Ritter-type reaction delivered amides 15 a and 15 b. Thereactions outlined in Scheme 3focus on the triazenes 3aa and 3ah.Further investigations with the racemic form of the norbornene-derived triazene 3da showed that similar substitution reactions are possible with other [2+ +2] cycloaddition products (see the Supporting Information for details). In most cases,g ood to excellent enantiospecificity was observed for these substitution reactions.H owever,d epending on the nucleophilicity of the trapping reactant and on the substituent on the cyclobutene,s ome erosion of the enantioselectivity was detected.…”

Nickel‐Catalyzed Asymmetric [2+2] Cycloaddition Reaction of Hetero‐Bicyclic Alkenes with Internal Alkynes

“…By employing ruthenium catalyst, the group of Tam has further studied the scope of alkynes using a number of internal electron‐deficient alkynes . Most recently, the group of Cramer uncovered the asymmetric [2+2] cycloaddition reaction of oxabenzonorbornadienes with 1‐alkynyl triazenes and elaborated the product by a range of nucleophiles . To the best of our knowledge, the asymmetric [2+2] cycloaddition reaction of azabenzonorbornadienes with internal alkynes have not been reported.…”

Versatile Catalytic Reactions of Norbornadiene Derivatives with Alkynes

“…In the year 2017, it was demonstrated that 1‐alkynyltriazenes ( 78 ) are suitable substrates for the enantioselective Ru‐catalyzed [2+2] cycloaddition reactions with bicyclic alkenes in the presence of a chiral cyclopentadienyl ligand ( 80 ) . The corresponding vinyltriazenes ( 79 ) were obtained in high yields with high enantioselectivities which could be replaced by a wide range of nucleophiles, hence providing an efficient access to a variety of chiral polycyclic compounds [Eq.…”