ChemInform Abstract: Enantioselective Synthesis of Macrocyclic Heterobiaryl Derivatives of Molecular Asymmetry by Molybdenum‐Catalyzed Asymmetric Ring‐Closing Metathesis.

Abstract

OKAYAMA, Y.; TSUJI, S.; TOYOMORI, Y.; MORI, A.; ARAE, S.; WU, W.-Y.; TAKAHASHI, T.; OGASAWARA*, M.; Angew. Chem., Int. Ed. 54 (2015) 16, 4927-4931, http://dx.doi.org/10.1002/anie.201500459 ; Dep. Chem. Sci. Eng., Fac. Eng., Kobe Univ., Nada, Kobe 657, Japan; Eng.) -Mais 32-052

Bithiophene with Winding Vine-shaped Molecular Asymmetry. Preparation, Structural Characterization, and Enantioselective Synthesis

“…9 Subsequent bromination at the 2-position of thiophene and Wittig methylenation lead to 2-bromo-3-(3-buten-1-yl)thiophene 4 (Scheme 1a). Bromothiophene 4 was also obtained from 3-methylthiophene (5) by sequential cationic and radical bromination reactions of 5 both with NBS to afford 2-bromo-3bromomethylthiophene (6) in 95% and 70% yields, respectively. Treatment of 6 with allyl Grignard reagent leads to 4 (85%), whose protocol has also been applied to the monomer synthesis of polythiophene with extremely high solubility in hydrocarbons (Scheme 1b).…”

“…Enantioselective RCM of bithiophene derivative was studied with a molybdenum-alkylidene complex in the presence of a chiral ligand composed of axially chiral biphenol or binaphthol derivatives. 5,17 The reaction was carried out with bithiophene 1 with 10 mol % Mo precursor 17 and 10 mol % chiral ligand L (Chart 1), which were mixed to generate the chiral complex in situ, in a benzene solution. 18,19 Several chiral ligands were examined, however, asymmetric induction was not observed in the RCM reaction with L1L3 as a ligand whereas the reaction proceeded smoothly.…”

“…We have also been successful in enantioselective preparation of such compounds of molecular asymmetry using a chiral molybdenum-alkylidene catalyst. 5 Our further concern turned to the design of other heterobiaryls showing related molecular asymmetry. Since we have been interested in developing CH functionalization reactions of five-membered heteroaromatic compounds 6 representative as thiophene derivatives 7 directed to advanced organic materials, it is intriguing to study if preparation of such vine-shaped compounds is possible in thiophene derivatives.…”

Double winding vine-shaped biphenyl with molecular asymmetry. Synthesis, structure, and properties

“…We have been studying the thus obtained cyclized product, which we call such a kind of chirality as the winding vineshaped molecular asymmetry. [11] The first preparation was shown with bis(benzo)imidazole [12] and several related hetero [13][14][15] and non-heteroaromatic [16] vine-shaped molecules have also been synthesized. We have also shown that the annulation reactions with nosylated diamine (nosyl: 2-nitro-benzenesulonyl) [17,18] with benzylic halide also furnishes another class of vine-shaped molecules and thus obtained compounds also showed molecular asymmetry.…”