Conformational analysis of functionalized sultines by nuclear magnetic resonance and x-ray crystallography. Application of a generalized Karplus equation (original) (raw)
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The Journal of Organic Chemistry, 2007
All reactions were done in an argon atmosphere using standard Schlenk techniques for the exclusion of moisture and air. Liquid reagents were distilled prior to use, while other commercial solids were used as supplied. NMR analyses were performed in CDCl3; chemical shifts are quoted in ppm relative to TMS (as referenced to residual CHCl3 δH = 7.26 or CDCl3 δC = 77.0) with coupling constants quoted in Hz. GC/MS was performed with 2 ml/min helium flow and following temperature program was used: 50 °C (2 min), 15 °C/min to 300 °C (3 min). General procedure for the formation of disulfides: To a solution of Burgess reagent (1.05 eq.) in benzene (1 molar) was added dropwise the corresponding thiol (1 equiv) dissolved in benzene at rt. The progress of the reaction was followed by GC/MS. After complete conversion of the starting material (approximately 30 minutes to 1 hour) the reaction mixture was filtered through a plug of silica (hexanes) The crude product was either triturated with hexanes or purified by flash column chromatography.
J. Chem. Soc., Perkin Trans. 1, 2001
Reaction between diethyl bromomalonate and 3-phenylpyrrolidine-2-thione yielded a vinylogous urethane by the Eschenmoser sulfide contraction. However, with 3-substituted piperidine-2-thiones, sulfur was retained in the products, and a range of bicyclic heterocycles, including bicyclic ketene S,N-acetals (2-alkylidene-1,3-thiazolidin-4ones) and stable thioisomünchnones, was isolated. A novel dimeric ketene S,N-acetal was characterised by X-ray crystallography.
An Adventitious Synthesis of 2,2′-Dipyrryl Disulfides
Australian Journal of Chemistry, 1999
Condensation of 1,2-diketones and a cyanothioacetamide gave hydroxy thiolactams which failed to give the expected 3-cyano methylene thiolactams on dehydration. Disulfides and a thiosulfonate were obtained from the dehydrations. A possible mechanism for their formation is proposed. The crystal structure of the disulfide 4,4′,5,5′-tetramethyl-1,1′-diphenyl-2,2′-disulfanediyldi-1H-pyrrole-3-carbonitrile (9) has been determined by X-ray diffraction.
J. Org.Chem. 1983, 48, 995-1000.pdf
J. Org. Chem. the relative ease of formation of the intermediates (IB > I H ) , while the slopes (greater a t lower pH) may reflect the relative ease of trapping of the two intermediates.
Helvetica Chimica Acta, 2002
The new six-membered-ring (2R)-10a-homobornane-10a,2-sultam (À)-3a was synthesized and its X-ray structural analysis was compared with that of the novel structure of the five-membered-ring (2R)-bornane-10,2sultam analogues (À)-1a,b as well as with that already published for the six-membered-ring trans-decalin-like sultam 4a. Based on DN** density-function calculations and X-ray crystallographic studies of the N-methylated analogues (À)-1e and 4b and by comparing with the conformation of the N-fluoro derivatives (À)-1c and ()-1d, the anomeric stabilization was estimated to be smaller than the 2.0 ± 2.5 kcal/mol earlier suggested. The direction of pyramidalization is rationalized in terms of H-bond and steric and electronic interactions and extended to the known toluenesultam derivatives 10a ± c. 2 ) For N lp through-bond and through-space directing interactions, initially suggested by M¸ller and Eschenmoser, see [10a]. For nonexhaustive more recent examples, see [10b ± g]. Cieplak also proposed a hyperconjugative influence of the N lp on the incipient bond-formation through the intermediacy of a sp 2 atom, see Schemes 85 and 86 as well as reference 105 in [11]. More recently, King et al. also suggested an anomeric stabilization [12a]