The use of sulfur ylides in the synthesis of 3-alkyl(aryl)thio-4-trifluoromethylpyrroles from mesoionic 4-trifluoroacetyl-1,3-oxazolium-5-olates
作者:Ryosuke Saijo、Masami Kawase
DOI:10.1016/j.tetlet.2012.03.130
日期:2012.5
In this report, we describe a new method for the synthesis of densely functionalized pyrroles. Reaction of mesoionic 1,3-oxazolium-5-olates with various S-ylides proceeds via nucleophilic addition followed by opening of the oxazole ring and subsequent cyclization to multisubstituted pyrroles bearing both a trifluoromethyl and alkyl(aryl)thio group at 3- and 4-positions.
NMR shift reagents for organic salts: Shift mechanism, bound shifts and structural analysis
作者:Thomas J. Wenzel、Kirk Cameron
DOI:10.1002/mrc.1260270805
日期:1989.8
Lanthanide tetrakis(β‐diketonate) anions are effective NMR shiftreagents for organic salts. The shifts in the 1H NMR spectra were analyzed and explained without invoking a contact shiftmechanism. The equilibria of the shiftreagent‐substrate complex was examined. No evidence was found for a 1:2 shiftreagent‐substrate complex. Bound shifts and association constants were determined for 1‐methyltetrahydrothiophenium
v.Braun; Truempler, Chemische Berichte, 1910, vol. 43, p. 550
作者:v.Braun、Truempler
DOI:——
日期:——
Grischkewitsch-Trochimowski, Zhurnal Russkago Fiziko-Khimicheskago Obshchestva, 1916, vol. 48, p. 952
作者:Grischkewitsch-Trochimowski
DOI:——
日期:——
13 C CP-MAS NMR studies of S -alkyl-1,4-dithianium salts: conformational motion in the solid state
作者:George W. Wagner、Yu-Chu Yang
DOI:10.1016/s0022-2860(98)00810-2
日期:1999.4
S-(2-chloroethyl)-1,4-dithianium, a persistent solid degradation product of mustard and the major constituent of ''mustard heels", exhibits motional line-broadening in its C-13 CP-MAS NMR spectrum. Variable temperature examination of the compound and a series of related S-alkyl-1,4-dithianium and thianium salts demonstrates the generality of the motion in these cyclic sulfonium salts. The underlying motional process for the carbons in the six-member rings cannot be attributed to ring rotation, the classical interpretation for cyclohexane, but is consistent with conformational motion. Solid dithiane, and the low temperature phases of cyclohexane and thiane were also studied by variable temperature C-13 MAS NMR to contrast the behavior of these neutral rings with the cyclic sulfonium salts. Distinguishing characteristics of the conformational mechanism include smaller E-a' s (2.3-6.1 kcal/mol) and line-broadening (400-600 Hz), compared to the ring-rotation mechanism operative in solid dithiane (12.9 kcal/mol, 1300 Hz) and the low-temperature phase of cyclohexane (11.4 kcal/mol, 925 Hz). The values for the low-temperature phase of thiane (3.8 kcal/mol, 525 Hz) are more consistent with conformational motion rather than hindered-rotation. (C) 1999 Elsevier Science B.V. ALI rights reserved.