Mechanism and origin of regioselectivity in Rh-catalyzed desymmetric [2 + 2 + 2] cycloaddition: charge versus π–π stacking interaction

Abstract

Density functional theory (DFT) calculations have been performed to investigate the mechanism and origin of the enantio- and regioselectivity of Rh-catalyzed desymmetric [2+2+2] cycloaddition of enynes with terminal alkynes. The...

Room Temperature Fluoranthene Synthesis through Cationic Rh(I)/H8-BINAP-Catalyzed [2 + 2 + 2] Cycloaddition: Unexpected Acceleration due to Noncovalent Interactions

“…Therefore, we conclude that the noncovalent interactions of the phenyl groups on both the substrates (diyne and monoyne) and the ligand in the cationic Rh(I) complex are another key to success for the present sterically demanding reaction by stabilizing the transition states rather than inducing steric repulsions. 21 The present computational studies explain well the experimental results in which sterically demanding diphenyl-substituted diyne 1a and diarylacetylenes showed high reactivity, contrary to the reactivity predicted by the steric bulkiness of the substrates.…”

Recent Advances in π-Stacking Interaction-Controlled Asymmetric Synthesis

“…The aromatic imines with electron-withdrawing substituents generally required longer reaction times and higher reaction temperatures than those with electron-donating groups. The reaction of electron-rich (S)-1-ethyl-4,5-dimethoxy-2-(4-tolylsulfinyl)benzene (19) and (E)-N-(4-methoxyphenyl)-1-phenylmethanimine (17b) stopped at the nucleophilic addition step in the presence of LDA as the base, generating the corresponding amine 20 as the final product after workup, rather than the desired The indoline skeleton is a ubiquitous moiety in the structures of many alkaloids and natural products. Indolines are generally considered to be key privileged structures for their diverse biological activities.…”

“…The aromatic imines with electron-withdrawing substituents generally required longer reaction times and higher reaction temperatures than those with electron-donating groups. The reaction of electron-rich (S)-1-ethyl-4,5-dimethoxy-2-(4-tolylsulfinyl)benzene (19) and (E)-N-(4-methoxyphenyl)-1-phenylmethanimine (17b) stopped at the nucleophilic addition step in the presence of LDA as the base, generating the corresponding amine 20 as the final product after workup, rather than the desired indoline derivative because the electron-rich arylsulfinyl with two strong electron-donating methoxy groups could not undergo the intramolecular aromatic nucleophilic substitution. Upon further treatment of the amine 20 with LHMDS, no reaction occurred as well, indicating that the electron-rich substrate indeed hardly underwent the intramolecular aromatic nucleophilic substitution even in a step-wise fashion.…”

“…Attractive π-stacking interactions between π-systems (both aromatic ring and other conjugated systems, even double and triple bonds) play various important roles in diverse phenomena, including the stabilization of biological macromolecules, such as the helical structures of DNA and tertiary structures of proteins, even the complexation of biomolecules and small organic compounds [1][2][3]; the stabilization of the complexation in host-guest systems [4,5]; and controlling selectivities in organic reactions [6][7][8][9]. They can not only control chemoselectivity [10][11][12][13][14] and regioselectivity [15][16][17][18][19] but also stereoselectivities, including diastereoselectivity and enantioselectivity, in diverse organic reactions [20,21]. In 1995, Jones and Chapman wrote a comprehensive review on the π-stacking effect in asymmetric synthesis [20].…”