Cyclic Diaryl λ³-Bromanes: A Rapid Access to Molecular Complexity via Cycloaddition Reactions

Abstract

Biaryls have widespread applications in organic synthesis. However, sequentially polysubstituted biaryls are underdeveloped due to their challenging preparation. Herein, we report the synthesis of dissymetric 2,3,2′,3′,4-substituted biaryls via pericyclic reactions of cyclic diaryl λ3-bromanes. The functional groups tolerance and atom economy allow access to molecular complexity in a single reaction step. Continuous flow protocol has been designed for the scale-up of the reaction, while postfunctionalizations have been developed taking advantage of the residual Br-atom.

Electrochemistry and Reactivity of Chelation‐stabilized Hypervalent Bromine(III) Compounds

“…The related isoelectronic hypervalent bromine(III) reagents exhibit stronger electrophilicity, better nucleofugality of the bromanyl unit, and more driving force for oxidations, [2–4] as evidenced by a series of unprecedented synthetic transformations involving oxidative coupling of alkynes and primary alcohols to conjugated enones, [5] Hofmann rearrangement of sulfonamides to the corresponding N ‐arylsulfamoyl fluorides, [6] regioselective C−H functionalization of non‐activated alkanes, [7,8a] and a rare Bayer‐Villiger‐type oxidation of open‐chain aliphatic aldehydes [9] . Recently, the application of diaryl‐ λ 3 ‐bromanes in catalysis [10] and in cycloaddition reactions [11] was also reported. Although these notable achievements underscore the remarkable synthetic potential of this reagent class, hypervalent bromine(III) chemistry appears to be underdeveloped in comparison to that of the iodine(III) counterparts.…”

Regiocontrol by Halogen Substituent on Arynes: Generation of 3-Haloarynes and Their Synthetic Reactions

“…31 The reaction of 74a and 74b with furan in the presence of Cs 2 CO 3 proceeded at room temperature to give the adducts 150a and 150b , respectively. 31b The [2+2] reaction between 74a and 3,4-dihydro-2 H -pyran 151 in the presence of Cs 2 CO 3 proceeded with excellent efficiency to give adducts 152 and 153 in 1.7:1 ratio. 31b Excellent regioselectivity was observed in the reaction of 74a with carboxylic acid 154 in the presence of Cs 2 CO 3 to give the product 155 in 99% yield.…”

Metal-free homo-/cross-anion–cation coupling of cyclic diaryl λ3-bromanes

“…19 They also reported the cycloaddition reactions of cyclic diaryl λ 3 -bromanes with π/2π-donors via an aryne-formation mechanism. 20 Cyclic diaryl λ 3 -bromanes can also be used as Lewis-acid/halogen-bonding organocatalysts. 21,22 Although these notable accomplishments have been made, the synthetic potential of cyclic diaryl λ 3 -bromanes is far from being fully exploited.…”