Rhodium‐Catalyzed Enantioselective Synthesis of Highly Fluorescent and CPL‐Active Dispiroindeno[2,1‐c]fluorenes

Abstract

II Synthesis of Starting Material1,1'-(Ethyne-1,2-diyl)bis(2-naphthaldehyde) (S) was synthesized by using the previously reported procedures. 11-Ethynyl-2-naphthaldehyde (S2a). In a Schlenk flask were dissolved PdCl2(PPh3)2 (0.5 mmol, 351 mg), CuI (1.0 mmol, 190 mg) and 1-bromo-2-naphthaldehyde S1a (10.0 mmol, 2.35 g) in THF (40 mL) followed by addition of trimethylsilylethyne (15.0 mmol, 2.1 mL) and Et3N (40 mL). The reaction mixture was stirred at reflux for 3 hours and then it was cooled down to 25 °C, filtered through a pad of Celite ® /silica, which was washed with Et2O. The filtrate was concentrated under reduced pressure. The residue was treated with K2CO3 pellets in a mixture of MeOH/water at 0 °C for 1 h. The resulting mixture was quenched with 1M HCl, extracted with CH2Cl2 (3× 100 mL), the combined organic fractions were washed with brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. Column chromatography of the residue on silica gel (19/1 hexanes/EtOAc) furnished 1.75 g (97%) of the title compound as a yellow solid.

Recommended Tests for the Self-Disproportionation of Enantiomers (SDE) to Ensure Accurate Reporting of the Stereochemical Outcome of Enantioselective Reactions

“…For other examples of high-quality experimental work on organo-catalytic and transition metal-catalyzed reactions, other recent papers [136,137] also stand out.…”

Cyclopenta-fused polyaromatic hydrocarbons: synthesis and characterisation of a stable, carbon-centred helical radical

“…According to the IUPAC definition, helicenes are ortho-fused polycyclic aromatic or heteroaromatic compounds in which all rings (minimum five) are angularly arranged so as to give helically shaped molecules, which are thus chiral, 17 while according to a more recent statement of the IUPAC, the term helicene might only be applicable to systems with at least six ortho-fused rings. 18 While non-conjugated 19 or cationic 20 helicenes containing five-membered rings have already been synthesized, no report came to our attention dealing with chiral CP-PAH helicenes (e.g., 7). Herein we present the synthesis of helical CP-PAHs, for which the above-mentioned properties might be supplemented by chiroptic properties.…”

Recent advances in the cascade reactions of enynols/diynols for the synthesis of carbo- and heterocycles

“…More recently, the same group also achieved the enantioselective synthesis of helically chiral diones 165 via the Rh(cod) 2 BF 4 /( S )-SEGPHOS® system-catalyzed intramolecular [2 + 2 + 2]-cyclotrimerization of triynediols 164 under mild conditions (Scheme 59). 70 This transformation proceeded with high enantioselectivity (er up to 93%) and high yields (up to 88%) of the final products under standard conditions. It should be noted that the obtained chiral diones 165 could be easily transformed into the corresponding helically chiral dispirodihydroindeno[2,1- c ]fluorenes.…”