Employed the pair (R)FeSulPhos (13)Cu(I) but usingdx.doi.org/10.1021/ja500071k | J. Am. Chem. Soc. 2014, 136, 2897Journal of your American Chemical Society Table 2. MetalCatalyzed 1,3Dipolar Cycloaddition of Azlactone 1b with [60]FullereneaArticleentry 1 2 3 4 five 6ametal salt/ligand AgOAc/(BINAP AgOAc/(R,R)BPE Cu(OAc)2/(R)FeSulPhos (R)DTBMSegPhos(AuOBz)two AgSbF6/(R,R)BPE CuI(OTf)d/(R)FeSulPhos CuI(OTf)d/(S)MefKetalPhossolvent (base) toluene (/) toluene (/) toluene (/) PhF/THF (/) PhF (Et3N) PhCl (Et3N) PhCl (Et3N)T ( ) 25 0 25 30 0 25conv.b ( ) 45 88 23 95 33 25eeb ( ) productc 50 (S)2b five (R)2b 40 (S)2b 87 (S)2b 70 (R)2b 90 (S)2bGeneral reaction conditions: A mixture of 0.01 mmol azlactone 1b, [60]fullerene (1 equiv), metal salt (20 mol ), ligand (20 mol ), and base (1 equiv) in 1.52 mL of indicated solvent is stirred for 1 hour at indicated temperature, then excess of DCC is added. bConversion and ee have been determined by HPLC evaluation. cAbsolute configuration has been assigned on the base of CD measurements. dCuI(OTf)benzene complex.triflate alternatively of acetate and Et3N as base. Similarly to the azomethine ylides addition onto [60]fullerene, this chiral ligand gave rise to the opposite pyrroline enantiomer with 25 conversion and 70 ee (entry six, Table 2). The enantioselectivity was located higher by utilizing (S)MefKetalPhos (14) as chiral ligand of Cu(I)triflatebenzene complicated because the pyrroline 2b is formed with 25 conversion and 90 ee (entry 7, Table 2).238749-50-3 custom synthesis It really is worthy to note that these outcomes represent the initial instance of enantioselective cycloaddition of munchnones catalyzed by a copper salt (Figure 4).Figure 4. Chiral ligands: (R,R)BPE (()1,2bis[(2R,5R)two,5diphenylphospholano]ethane), (12), (R)FeSulPhos ((Rp)2(tertbutylthio)1(diphenylphosphino)ferrocene), (13), (S)MefKetalPhos (1,1bis[(2S,3S,4S,5S)two,5dimethyl3,4Oisopropylidene3,4dihydroxyphospholanyl]ferrocene), (14).Scope in the Catalytic Processes with Distinct Oxazolones. Once optimized the conditions for the organocatalytic and for the metalcatalyzed [3 2] cycloaddition of oxazolones onto [60]fullerene, we studied the scope in the reaction. The distinctive oxazolones applied have been prepared from amino acids including glycine, alanine, and phenylalanine and benzoic acid or derivatives endowed with one particular or three hydrocarbon chains. The results obtained for each methodologies, applying distinctive azlactones 1aj as 1,3dipoles are shown in Table 3. Generally, metalbased chiral catalysts gave rise towards the desired pyrrolinofullerene derivatives 2aj with moderate to good conversions and high enantiomeric excesses.Trifluoromethanesulfonic acid (silver) Chemical name The asymmetric induction sense is fully controlled by suitable choice of your metal complicated, and enantioselectivity is unaffected, or small influenced, by the substitution of your starting oxazolone.PMID:24670464 Thus, azlactones 1a, 1b, or 1i bring about the formation of 2a, 2b, and 2i with higher enantioselectivities each with silver or copperchiral complexes (entries 1, two, and 9, Table 3). Furthermore, exceptional enantiomeric excesses were observed for the pyrrolinofullerenes 2b and 2c (90 and 96 , entries 2 and three, Table three) with CuI(OTf)benzene complex/(S)MefKetalPhos (14)/Et3N for the (S)two merchandise. It is actually worth mentioning that within the latter case, the presence of 3 huge alkoxy chains in the aromatic moiety of 2c supplied enough solubility to enable the direct isolation on the absolutely free carboxylic acid pyrrolinofullerene derivative without the need of employing DCC for the further esterification (see SI). W.
