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Azodioxy compounds as precursors for C-radicals and their application in thermal styrene difunctionalization.

ABSTRACT: An atom-economic thermal α,β-difunctionalization of various styrenes with readily prepared azodioxy compounds is reported. Mechanistic studies reveal that the starting azodioxy compounds can thermally be cleaved to the corresponding C-nitroso compounds, which under these thermal conditions further homolyze to generate reactive C-radicals along with the persistent NO radical. In the presence of a styrene, C-radical addition with subsequent nitrosylation followed by tautomerization is occurring, resulting in an overall styrene β-alkylation-α-oximation reaction.

SUBMITTER: Ploger S

PROVIDER: S-EPMC9400666 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Azodioxy compounds as precursors for C-radicals and their application in thermal styrene difunctionalization.

Plöger Stefanie S Mück-Lichtenfeld Christian C Daniliuc Constantin G CG Studer Armido A

Chemical science 20220805 33

An atom-economic thermal α,β-difunctionalization of various styrenes with readily prepared azodioxy compounds is reported. Mechanistic studies reveal that the starting azodioxy compounds can thermally be cleaved to the corresponding C-nitroso compounds, which under these thermal conditions further homolyze to generate reactive C-radicals along with the persistent NO radical. In the presence of a styrene, C-radical addition with subsequent nitrosylation followed by tautomerization is occurring, r ...[more]

PMID: 36091902

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Project description:A study on the α-(difluoromethyl)styrene (DFMST) reactivity under conventional radical copolymerization conditions is presented. Although the homopolymerization of DFMST failed, its radical bulk copolymerization with styrene (ST) led to the synthesis of fluorinated aromatic polymers (FAPs). The resulting novel poly(DFMST-co-ST) copolymers were characterized by 1H, 19F and 13C NMR spectroscopies that evidenced the successful incorporation of DFMST units into copolymers and enabled the assessment of their respective molar percentages (10.4-48.2 mol%). The molar masses were in the range of 1900-17 200 g mol-1. The bulkier CF2H group in the α-position induced the lower reactivity of the DFMST comonomer. ST and DFMST monomer reactivity ratios (r DFMST = 0.0 and r ST = 0.70 ± 0.05 at 70 °C) were determined based on linear least-square methods. These values indicate that DFMST monomer is less reactive than ST, retards the polymerization rate, and thus reduces the molar masses. Moreover, the thermal properties (T g, T d) of the resulting copolymers indicate that the presence of DFMST units incorporated into poly(ST) structure promotes an increase of the T g values up to 109 °C and a slightly better thermal stability than that of poly(ST). Additionally, the thermal decomposition of poly(DFMST-co-ST) copolymer (10.4/89.6) was assessed by simultaneous thermal analysis coupled with Fourier-transform infrared spectroscopy and thermogravimetric analysis coupled with mass spectrometry showing that H2O, CO2, CO and styrene were released. The surface analysis was focused on the effects of the -CF2H group at the α-position of styrene comonomers on surface free energy of the copolymer films. Water and diiodomethane contact angle (CA) measurements confirmed that these copolymers (M n = 2300-17 200 g mol-1) are not exactly the same as polystyrenes (M n = 2100-21 600 g mol-1) in the solid state. The CA hysteresis for poly(ST) (6-8°) and poly(DFMST-co-ST) copolymers (3-5°) reflected these differences even more accurately.

Dataset Information

Azodioxy compounds as precursors for C-radicals and their application in thermal styrene difunctionalization.

Publications

Azodioxy compounds as precursors for C-radicals and their application in thermal styrene difunctionalization.

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