86409-86-1Relevant academic research and scientific papers
A convenient new route to piperidines, pyrrolizidines, indolizidines, and quinolizidines by cyclization of acetylenic sulfones with β- and γ-chloroamines. Enantioselective total synthesis of indolizidines (-)-167B, (-)-209D, (-)-209B, and (-)-207A
Back, Thomas G.,Nakajima, Katsumasa
, p. 4543 - 4552 (2007/10/03)
The methyl esters of (L)-phenylalanine and (L)-methionine underwent conjugate additions via their free amino groups to 1-(p-toluenesulfonyl)hexyne, followed by intramolecular acylation of the corresponding enamide anions and tautomerization to afford 2-benzyl-5-n-butyl-3-hydroxy-4-(p-toluenesulfonyl)pyrrole and 5-n-butyl-3-hydroxy-2-(2-methylthioethyl)-4-(p-toluenesulfonyl)pyrrole, respectively. The conjugate additions of a series of acyclic and cyclic secondary β- and γ-chloroamines to acetylenic sulfones proceeded similarly under mild conditions. The resulting adducts were deprotonated with LDA in THF at -78 °C, and the resulting sulfone-stabilized carbanions underwent intramolecular alkylation to afford cyclic enamine sulfones. Thus, acyclic γ-chloroalkylbenzylamines afforded the corresponding 2- or 2,6-disubstituted piperidines, while 2-(chloromethyl)-pyrrolidines, 2-(2-chloroethyl)pyrrolidines, 2-(chloromethyl)piperidines, and 2-(2-chloroethyl)-piperidines produced the corresponding 3-substituted pyrrolizidines, 5- or 3-substituted indolizidines, and 4-substituted quinolizidines, respectively. 8-Methyl-5-substituted indolizidines were also prepared from the appropriate methyl-substituted chloroamine precursor. Enantioselective syntheses were achieved by employing chiral chloroamines derived from amino acids or other enantiopure precursors. Further transformations of several of the products provided concise syntheses of four dendrobatid alkaloids. Thus, reduction of (8aS)-5-n-propyl-6-(p-toluenesulfonyl)-Δ-indolizidine with sodium cyanoborohydride in trifluoroacetic acid, followed by reductive desulfonylation, afforded (-)-indolizidine 167B. The corresponding 5-n-hexyl derivative similarly produced (-)-indolizidine 209D, while (-)-(8R,8aS)-8-methyl-5-n-pentyl-6-(p-toluenesulfonyl)-Δ5,6-indolizidine furnished (-)-indolizidine 209B. Finally, the similar reduction and debenzylation of (-)-(8R,8aS)-5-(2-benzyloxyethyl)-8-methyl-6-(p-toluenesulfonyl)-Δ-indolizid ine produced the corresponding 5-hydroxyethyl indolizidine. This was subjected to chlorination of the alcohol group with thionyl chloride and substitution with a higher order allyl cuprate reagent to afford (-)-indolizidine 207A.
Selenosulfonation of Acetylenes: Preparation of Novel β-(Phenylseleno)vinyl Sulfones and Their Conversion to Acetylenic and β-Functionalized Sulfones
Back, Thomas G.,Collins, Scott,Kerr, Russell G.
, p. 3077 - 3084 (2007/10/02)
The 1,2-additions of Se-phenyl p-tolueneselenosulfonate (1) to acetylenes under mild conditions afford β-(phenylseleno)vinyl sulfones 3, generally in high yields.The reaction is highly regioselective (anti-Markovnikov) and stereoselective (anti) and proceeds via a free-radical chain mechanism initiated by the thermolysis of the selenosulfonate.The oxidation of β-(phenylseleno)vinyl sulfones with m-chloroperbenzoic acid generates the corresponding selenoxides 4, which undergo syn or base-catalyzed elimination to furnish acetylenic sulfones 5.Base-catalyzed alcoholyses of selenoxides 4 in methanol or ethylene glycol produce β-keto sulfone ketals 8 or 10, respectively.Free β-keto sulfones 11 are formed by the acid-catalyzed hydrolysis of the corresponding β-(phenylseleno)vinyl sulfones 3.
