Photo‐Fries Rearrangement of Carbazol‐2‐yl Sulfonates: Efficient Tool for the Introduction of Sulfonyl Groups into Polycyclic Aromatic Compounds

Abstract

Systematic studies on the photo-Fries rearrangement of different 9H-carbazol-2-yl sulfonates 2 have shown that this type of conversion can be readily used for the preparative-scale introduction of alkyl-or arylsulfonyl groups into polycyclic aromatic compounds under very mild conditions. A series of new 1-sulfonyl-(3) or 3-sulfonyl-9H-carbazoles (4) were prepared in medium-to-good yields, and characterized by UV/VIS, 1 H-NMR, and 13 C-NMR spectroscopy, as well as by elemental analysis. Effects of irradiation wavelength, solvent polarity, presence or absence of O 2 , and photosensitizers were studied in detail.

Synthetic Methods for Compounds Having CF3–S Units on Carbon by Trifluoromethylation, Trifluoromethylthiolation, Triflylation, and Related Reactions

“…In 2006, Bonesi and co-workers reported the photo-Fries rearrangement of 9H-carbazol-2-yl triflate giving ortho-rearranged products (eq a, Scheme 107). 413 Our group reported the LDA (lithium diisopropylamine)-mediated anionic thia-Fries rearrangement for the synthesis of heteroaromatic triflones including oxindole, pyrazolone, pyridine, and quinoline triflones (eq b, Scheme 107). 414 An unusual NaH-mediated remote anionic 1,5-thia-Fries rearrangement reaction was developed by our group (eq c, Scheme 107).…”

“…The rearrangement of heteroaryl triflates provides another synthetic method to produce various heteroaryl triflones (Scheme ). In 2006, Bonesi and co-workers reported the photo-Fries rearrangement of 9 H -carbazol-2-yl triflate giving ortho-rearranged products (eq a, Scheme ) . Our group reported the LDA (lithium diisopropylamine)-mediated anionic thia-Fries rearrangement for the synthesis of heteroaromatic triflones including oxindole, pyrazolone, pyridine, and quinoline triflones (eq b, Scheme ) .…”

Selectivity in the Photo-Fries Rearrangement of Some Aryl Benzoates in Green and Sustainable Media. Preparative and Mechanistic Studies

“…Anderson and Reese have discovered the photoreaction where a homolytic fragmentation of a carbon–heteroatom bond is involved, i.e., C–O, C–S, and C–N, of esters, thioesters and amides, respectively . The photo-Fries rearrangement proceeds via a well-established radical mechanism, mainly occurring through the excited singlet state. , Typically, the photoinduced Fries rearrangement reaction of (hetero)­aryl benzoates in homogeneous media affords ortho- and para- regioisomers as well as the corresponding phenols (Scheme ). , …”

Pd-Catalyzed Synthesis of Aryl and Heteroaryl Triflones from Reactions of Sodium Triflinate with Aryl (Heteroaryl) Triflates

“…The widespread application of traditional methods to prepare aryl­(heteroaryl) triflones such as Friedel–Crafts triflylations, aryl Grignard additions to (CF 3 SO 2 ) 2 O, anionic thia-Fries rerrangements, − oxidation of aryltrifluoromethyl sulfides, − nucleophilic trifluoromethylation reactions − cycloaddition reactions, − thermal decomposition, etc. has been limited due to low yields, poor substrate scope, use of expensive reagents, harsh reaction conditions, formation of isomeric products, and incompatibility of reaction conditions with common organic functional groups .…”