Synthesis of Bridging Chiral p–tert‐Butylcalix[4]arenes with One and Two Carbamoyl Bridge‐Substituents through Anionic Ortho‐Fries Rearrangement

Abstract

Bridging chiral p‐tert‐butylcalix[4]arenes (p‐t‐Bu‐BCC's) with different N‐substituted carbamoyl bridge‐substituents (N,N‐dimethylcarbamoyl, N,N‐diethylcarbamoyl and morpholinocarbonyl) were successfully prepared through anionic ortho‐Fries rearrangement from mono‐O‐carbamates of 1,3‐dipropyl‐p‐tert‐butylcalix[4]arene in 65–75% yield. In addition, p‐t‐Bu‐BCC with two N,N‐dimethylcarbamoyl bridge‐substituents was produced by this method from mono‐O‐carbamate of p‐t‐Bu‐BCC with one N,N‐dimethylcarbamoyl bridge‐substituent in 71% yield. However, the synthesis of p‐t‐Bu‐BCC with additional carbamoyl bridge‐substituents using this method could not be attempted, as the required rearrangement precursor failed to be synthesized. Finally, the racemic p‐t‐Bu‐BCC with morpholinocarbonyl bridge‐substituent was optically resolved into a pair of enantiomers, whose absolute configurations were determined through ROESY analysis and ECD comparison.

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

“…Ma et al . presented bridging chiral p - tert -butylcalix­[4]­arenes ( p - t -Bu-BCC’s) with various N -substituted carbamoyl bridge-substituents ( N , N -dimethylcarbamoyl, 354a ; N , N -diethylcarbamoyl, 354b ; morpholinocarbonyl, 354c ) by A o F rearrangement from mono- O -carbamates of 1,3-dipropyl- p - tert -butylcalix­[4]­arene 353 in 65–75% yield (Scheme ).…”

“…Ma et al. 365 presented bridging chiral p - tert -butylcalix[4]arenes ( p - t -Bu-BCC’s) with various N -substituted carbamoyl bridge-substituents ( N , N -dimethylcarbamoyl, 354a ; N , N -diethylcarbamoyl, 354b ; morpholinocarbonyl, 354c ) by A o F rearrangement from mono- O -carbamates of 1,3-dipropyl- p - tert -butylcalix[4]arene 353 in 65–75% yield ( Scheme 86 ). In addition, p - t -Bu-BCC with two N , N -dimethylcarbamoyl bridging substituents 356a was also prepared by this method from mono- O -carbamate of p - t -Bu-BCC 355a with one N , N -dimethylcarbamoyl bridging substituent in 71% yield.…”

Calix[4]arene Bridge Mononitration with tert-Butyl Nitrite: Synthesis of Bridging Chiral p-tert-Butylcalix[4]arene with a Mononitro Bridge Substituent

“…The constructions of bridging chiral calixarenes with different bridge substituents are a key step in their research. Until now, only bridging chiral calix[4]­arenes with hydroxyl and methoxyl, carbamoyl, and aminomethyl bridge substituent were synthesized. Hence, it is highly significant to synthesize structurally diverse bridging chiral calix[4]­arenes.…”

“…However, the derivatization methods of the methylene bridges are rather poorly developed. The frequently reported methods to derive the bridges are limited in bromination, lithiation, oxidation, and ortho -Fries rearrangement (Figure a–d). Liu’s and Wei’s groups recently reported the nitration of 8-methylquinoline and 2-oxindole with tert -butyl nitrite ( t -BuONO), respectively .…”

Mononitration of a Calix[4]arene Methylene Bridge: Synthesis and Preliminary Catalysis Performances of Bridging Chiral p-tert-Butylcalix[4]arenes with a Monoamino Bridge Substituent in a 1,3-Alternate Conformation

“…Bridging chiral calixarenes have potential to be excellent chiral organocatalysts due to their macrocyclic structure and bridging point chirality . As a member of intrinsically chiral calixarenes, bridging chiral ones are rarely studied in their synthesis and properties compared to inherently chiral ones …”