Enantiospecific Generation and Trapping Reactions of Aryne Atropisomers

Abstract

Enantioenriched aryne atropisomers having a biaryl stereogenic axis vicinal to the reactive triple bond are demonstrated to exist. These reaction intermediates are easily produced in situ and can undergo the standard aryne cycloaddition chemistry in an enantiospecific manner. Notably, the aryne atropisomers herein have allowed the practical syntheses of a small nanographene as well as some triptycene and anthracene derivatives that embed stereogenic axes of controlled absolute configurations.

Biobased C6-Furans in Organic Synthesis and Industry: Cycloaddition Chemistry as a Key Approach to Aromatic Building Blocks

“…A broad scope of benzoannulated 7-oxanorbornenes can be obtained via this approach. The utilization of diarynes (Table ) and polycyclic arynes (Table ) leads to the formation of condensed polycyclic systems. …”

Determination of the Rate Constant of the [4 + 2] Cycloaddition Between an Aryne Atropisomer and Furan in Solution

“…The enantiomerization barriers of several aryne atropisomers were previously evaluated by computational DFT methods, typically B3LYP-D3/6-311++G­(d,p) . It was identified that the barriers to enantiomerization of aryne atropisomers are significantly lower than the barriers to enantiomerization of the corresponding biaryl derivatives having two C­(sp 2 )–H bonds in place of the aryne triple bond due to a lack of repulsive van der Waals interactions with the H atom ortho to the stereogenic axes.…”

“…It was supposed that the nonracemic aryne atropisomer ( aS )- 1 could be generated enantiospecifically from the nonracemic iodoaryl triflate precursor ( aS )- 7 (Scheme ). , The synthesis of ( aS )- 7 was accomplished by a Suzuki coupling between bromide 3 and boronic acid 4 for the construction of the biaryl axis in 5 , followed by deprotection to give intermediate A (not shown) and ortho-iodination to afford racemic 6 . The barrier to enantiomerization of 6 was estimated at 196.8 kJ·mol –1 by DFT methods (see Supporting Information, Figure S3), and the atropisomers of 6 could be resolved by semi-preparative HPLC methods to obtain enantiomerically pure materials.…”

“…The enantiospecific generation and trapping reactions of nonracemic aryne atropisomers based on a 1-phenylnaphthalene backbone were reported recently (Scheme a) . In these cases, the rates of reaction of the aryne atropisomers are greater than their rates of enantiomerization by several orders of magnitude, which allowed for highly enantiospecific reactions.…”

Chiral Triptycenes: Concepts, Progress and Prospects

“…Similarly, the conformations of 9,9′‐bitriptycyl derivatives with the general formula XCH 2 ‐CH 2 X and XYZC‐CXYZ have been studied. Very recently, a new strategy has been explored using an enantioenriched aryne atropisomers for the synthesis of chiral triptycenes [8d] …”