Gold‐Catalyzed Regiospecific Annulation of Unsymmetrically Substituted 1,5‐Diynes for the Precise Synthesis of Bispentalenes

Abstract

Precisec ontrol of the selectivity in organic synthesis is importantt oa ccess the desired molecules. We demonstrate ar egiospecific annulation of unsymmetrically substituted 1,2-di(arylethynyl)benzened erivatives for ag eometrycontrolled synthesis of linear bispentalenes, which is one of the promisings tructures for materials cience.Ag old-catalyzed annulation of unsymmetrically substituted 1,2-di(arylethynyl)benzene could produce two isomeric pentalenes, but both electronic and steric effectso nt he aromatics at the terminal position of the alkyne prove to be crucial for the selectivity;e speciallyaregiospecific annulationw as achieved with sterically blockeds ubstituents;n amely,2 ,4,6-trimetylb enzene or 2,4-dimethyl benzene. This approache nables the geometrically controlled synthesis of linear bispentalenes from 1,2,4,5-tetraethynylbenzeneo r2 ,3,6,7-tetraethynylnaphthalene. Moreover,t he annulation of as eries of tetraynesw ith ad ifferent substitution pattern regioselectively provided the bispentalene scaffolds.Ac omputational study revealed that this is the result of ak inetic control induced by the bulky NHC ligands.

Unsymmetrical Thienopentalenes: Synthesis, Optoelectronic Properties, and (Anti)aromaticity Analysis

“…To control the selectivity of the reaction, one of the phenylacetylenes was replaced with 4-ethynylanisole that was expected to promote the regioselective annulation and facilitate the purification (Scheme ). Indeed, after performing the gold-catalyzed annulation on compound 19 , a single isomer of V (PMP) could be isolated as a green solid.…”

Homogeneous and Heterogeneous Gold Catalysis for Materials Science

“…For a more selective synthesis of these "S-shaped" bispentalenes, a modification of the aryl substituents turned out to be successful. 329 Blocking the ortho positions by using two mesitylene substituents (100), bispentalenes 101 were selectively obtained in 81 and 86% yield (Scheme 63).…”

“…To further extend the π-system, different bidirectional approaches were successfully conducted also. − When using tetrayne 96 as a starting material, the angulated bispentalene 97 (“U-shaped”) was obtained in remarkable yields. The conceivable regioisomer 98 (“S-shaped”) was indeed not observed.…”

Unprecedented Use of NHC Gold (I) Complexes as Catalysts for the Selective Oxidation of Ethane to Acetic Acid

“…It is well-recognized that N-heterocyclic carbene (NHC) ligands have played an increasingly significant role in designing homogeneous catalysts. NHC metal complexes are able to catalyze different types of reactions, such as alkene activation, alkyne hydration, hydroamination, hydrosilylation or C–C couplings [ 1 , 2 , 3 , 4 , 5 ].…”