3709-34-0Relevant academic research and scientific papers
Scope and mechanism for Lewis acid-catalyzed cycloadditions of aldehydes and donor-acceptor cyclopropanes: Evidence for a stereospecific intimate ion pair pathway
Pohlhaus, Patrick D.,Sanders, Shanina D.,Parsons, Andrew T.,Li, Wei,Johnson, Jeffrey S.
, p. 8642 - 8650 (2008/12/23)
In this work, the one-step diastereoselective synthesis of cis-2,5-disubstituted tetrahydrofurans via Lewis acid catalyzed [3 + 2] cycloadditions of donor-acceptor (D-A) cyclopropanes and aldehydes is described. The scope and limitations with respect to both reaction partners are provided. A detailed examination of the mechanism has been performed, including stereochemical analysis and electronic profiling of both reactants. Experimental evidence supports an unusual stereospecific intimate ion pair mechanism wherein the aldehyde functions as a nucleophile and malonate acts as the nucleofuge. The reaction proceeds with inversion at the cyclopropane donor site and allows absolute stereochemical information to be transferred to the products with high fidelity. The mechanism facilitates the stereospecific synthesis of a range of optically active tetrahydrofuran derivatives from enantioenriched D-A cyclopropanes.
S-Ethenylsulfoximine Derivatives. Reagents for Ethylenation of Protic Nucleophiles
Johnson, Carl R.,Lockard, James P.,Kennedy, Eugene R.
, p. 264 - 271 (2007/10/02)
The preparation of S-vinyl and S-(2-substituted)ethenyl derivatives of sulfoximines is described.Vinyl-, (2-phenylethenyl)-, (2,2-diphenylethenyl)-, (2-methyl-1-propenyl)-, (dimethylamino)phenyloxosulfonium fluoroborates were found to undergo an addition-elimination reaction sequence with protic nitrogen and carbon nucleophiles, resulting in ethylenation of the nucleophile and N,N-dimethylbenzenesulfinamide.Primary amines gave aziridines, enamines gave cyclopropyl derivatives of iminium salts or pyrrolidinium salts, anions of active methylene compounds gave dihydrofurans and/or cyclopropanes, and anions of nitroalkanes gave cyclic nitronic esters and/or nitrocyclopropanes.In several cases vinyl salts were generated in situ from β-methoxyoxosulfonium salts.Treatment of (-)-(S)-dimethylamino)phenyl(trans-2-phenylethenyl)oxosulfonium fluoroborate with methyl cyanoacetate in methanol containing sodium methoxide gave, in 81percent yield, (+)-(1S,2R)-methyl 1-cyano-2-phenylcyclopropanecarboxylate of 25.5percent optical purity.The same salt upon treatment with methyl nitroacetate gave, in 95percent yield, methyl 4-phenyl-3-isoxazolinecarboxylate 2-oxide with 33percent enantiomeric excess.Cyclopropanes were formed upon treatment of S-methyl-S-(trans-2-phenylethenyl)-N-(p-tolylsulfonyl)sulfoximine with anions of active methylene compounds.
