1. Synthesis of Spirocyclic Cyclobutenes through Desulfinative Spirocyclisation of gem-Bis(triflyl)cyclobutenes
Shoki Hoshikawa, Hikaru Yanai, Takashi Matsumoto Chemistry. 2022 Jun 10;28(33):e202200704. doi: 10.1002/chem.202200704. Epub 2022 May 16.
A two-step synthesis of less accessible spiro[cyclobutene-1,9'-fluorene] compounds from biaryl-alkynes and 2-(2-fluoropyridin-1-ium-1-yl)-1,1-bis((trifluoromethyl)sulfonyl)ethan-1-ide, which serves as a potent precursor for outstandingly electrophilic Tf2 C=CH2 , has been developed. This synthetic methodology includes selective formation of gem-bis(triflyl)cyclobutenes from biaryl-alkynes and Tf2 C=CH2 followed by desulfinative spirocyclisation mediated by 1,1,1,3,3,3-hexafluoroisopropyl alcohol (HFIP). Besides, on the basis of the chameleonic reactivity of sulfone functionality, several derivatisations of triflylated spiro[cyclobutene-1,9'-fluorene] products have been successfully achieved.
2. Simple organofluorine compounds giving field-dependent 13C and 19F NMR spectra with complex patterns: higher order effects and cross-correlated relaxation
Lawrence B Alemany, Thomas B Malloy Jr, Megan M Nunes Magn Reson Chem. 2010 Nov;48(11):882-91. doi: 10.1002/mrc.2684.
The CF(3) signals in the (13)C{(1)H} spectrum of 1,1,1,3,3,3-hexafluoroisopropyl alcohol and the (CF(3))(2) CH signals in the corresponding triflate exhibit much greater complexity than might first be expected. The same holds for the (13)C satellites in the (19)F spectra. Complex patterns appear because of higher order effects resulting from the combination of a relatively large four-bond (19)F-(19)F J coupling in the ((13)CF(3))(12)CH((12)CF(3))-containing isotopomer and a typical large one-bond (13)C/(12)C isotope effect on the (19)F chemical shift. This complexity cannot be eliminated at very high magnetic field strengths. The triflate (CF(3))(2)CH-O-SO(2)CF(3) presents still additional complexity because of the presence of two different types of CF(3) groups exhibiting (6)J(FF) in any of the isotopomers and the chemical shift differences in hertz between the various (19)F signals in the two different (13)CF(3)-containing isotopomers. In addition, the presence of a small (5)J(CF) in the ((13)CF(3))((12)CF(3))(12)CH-O-SO(2) (12)CF(3) isotopomer is revealed only through simulations. The hexafluoroisopropyl CF(3) groups in the alcohol and triflate and the SO(2)CF(3) group in the triflate apparently provide the first examples of cross-correlated relaxation in (13)CF(3) groups. An analysis of the spectra in the context of previously reported work highlights the novel aspects of our findings. In particular, for each part of the complex hexafluoroisopropyl CF(3) quartet, peak height and linewidth variations resulting from cross-correlated relaxation are observed. These variations within a group of (13)C signals reflect different spin-lattice and spin-spin relaxation rates for the transitions within that group arising from higher order coupling effects.
3. Anodic Oxidation of 18 Halogenated and/or Methylated Derivatives of CB11H12
Abdul Wahab, Christos Douvris, Jiří Klíma, Filip Šembera, Juri Ugolotti, Jiří Kaleta, Jiří Ludvík, Josef Michl Inorg Chem. 2017 Jan 3;56(1):269-276. doi: 10.1021/acs.inorgchem.6b02126. Epub 2016 Dec 12.
Anodic oxidation of [CB11H12]- and 18 of its halogenated and/or methylated derivatives was examined. Reversible oxidation was found for four of the anions in liquid SO2 and for four more in 1,1,1,3,3,3-hexafluoroisopropyl alcohol. The oxidation occurred at ~1 V (for [CB11Me12]-) up to more than 4 V (for [1-H-(2-6)-F5-(7-12)-(CF3)6-CB11]-) relative to ferrocene/ferricinium. The anodic peak potentials are reproduced by a set of additive position-sensitive substituent increments.
