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Conventional vs. Microwave- or Mechanically-Assisted Synthesis of Dihomooxacalix[4]arene Phthalimides: NMR, X-ray and Photophysical Analysis.


ABSTRACT: Direct O-alkylation of p-tert-butyldihomooxacalix[4]arene (1) with N-(bromopropyl)- or N-(bromoethyl)phthalimides and K2CO3 in acetonitrile was conducted under conventional heating (reflux) and using microwave irradiation and ball milling methodologies. The reactions afforded mono- and mainly distal di-substituted derivatives in the cone conformation, in a total of eight compounds. They were isolated by column chromatography, and their conformations and the substitution patterns were established by NMR spectroscopy (1H, 13C, COSY and NOESY experiments). The X-ray structures of four dihomooxacalix[4]arene phthalimide derivatives (2a, 3a, 3b and 5a) are reported, as well as their photophysical properties. The microwave (MW)-assisted alkylations drastically reduced the reaction times (from days to less than 45 min) and produced higher yields of both 1,3-di-substituted phthalimides (3a and 6a) with higher selectivity. Ball milling did not reveal to be a good method for this kind of reaction.

SUBMITTER: Miranda AS 

PROVIDER: S-EPMC7998390 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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Conventional vs. Microwave- or Mechanically-Assisted Synthesis of Dihomooxacalix[4]arene Phthalimides: NMR, X-ray and Photophysical Analysis.

Miranda Alexandre S AS   Marcos Paula M PM   Ascenso José R JR   Robalo M Paula MP   Bonifácio Vasco D B VDB   Berberan-Santos Mário N MN   Hickey Neal N   Geremia Silvano S  

Molecules (Basel, Switzerland) 20210310 6


Direct <i>O</i>-alkylation of <i>p-tert</i>-butyldihomooxacalix[4]arene (<b>1</b>) with <i>N</i>-(bromopropyl)- or <i>N</i>-(bromoethyl)phthalimides and K<sub>2</sub>CO<sub>3</sub> in acetonitrile was conducted under conventional heating (reflux) and using microwave irradiation and ball milling methodologies. The reactions afforded mono- and mainly distal di-substituted derivatives in the cone conformation, in a total of eight compounds. They were isolated by column chromatography, and their con  ...[more]

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