Synthesis of some thiochromeno[4,3-c]- and [3,4-c]-pyrazoles

A facile route to pyrroles, isoindoles and hetero fused analogues

“…From our research projects on chromanones and thiochromanones we had access to a range of 3-hydroxymethylene-(thio)chromanones 18c-f. 22,23 The enamino acids, 19h and 19i, derived from glycine and the 3-hydroxymethylenebenzopyrans 18c and 18d respectively, cyclised to give the benzopyrano [3,4c]pyrroles 20h and i. The benzopyrano[3,4-c]pyrrole ring system has recently been accessed by the photogeneration of radicals from α-stannyl ethers and their conjugate addition to enones, 24 through the displacement of the iron residue in 4-[η 5 -cyclopentadienyl(dicarbonyl)iron]-2H-chromene-3-carbaldehyde with primary amines 25 and by the Fischer-Fink reaction of 4-chloro-3-formylcoumarins with amino acid esters.…”

3-Pyrazolines (2,3-dihydro-1H-pyrazoles): synthesis, reactivity, and physical and biological properties

“…5). 38 This result is very unexpected and the compounds were characterized by an NH band in the IR spectra and by two (30)(31)(32)(33) or three (29) signals in the 1 H NMR spectra due to the NH and the saturated CH at position 5. We have tried to repeat this work without success.…”

“…Although Kenny and Robinson were not cited, 27,28 other authors employed Baldwin's rules to explain the results obtained with methylhydrazine (21, R 1 = CH3, R 2 = H). 30 The use of Baldwin's rules by Kenny and Robinson 27,28 was questioned by List in 2010; he suggested that a more plausible mechanism would involve a pericyclic 6π-electrocyclization. 31 Although both mechanisms will lead to different stereoisomers, the N-phenyl inversion will make them indistinguishable (Figure 4).…”

Expedient synthesis of highly substituted 3,4-dihydro-1,2-oxathiine 2,2-dioxides and 1,2-oxathiine 2,2-dioxides: revisiting sulfene additions to enaminoketones

“…Routine 1 H NMR (400 MHz) and 13 C NMR (100 MHz) spectra were recorded on a Bruker Avance DPX400 instrument in CDCl 3 . Variable Temperature 1 H NMR (500 MHz) and 13 30 (24) and (Z)-3-(hydroxymethylene)-2,2,6-trimethylthiochroman-4-one 31 (25) and isothiochromanone 32 (32) were prepared according to previously reported procedures. 4-(Dimethylamino)-3-(2-fluorophenyl)but-3-en-2-one (15) was prepared according to the procedure described by Kozmin et al, for the preparation of 4-(dimethylamino)-3-phenylbut-3-en-2-one.…”