Synthesis of (3aS-cis)-(−)- and (3aR-cis)-(+)-debromoflustramine B

A Divergent Approach to the Diastereoselective Synthesis of 3,3‐Disubstituted Oxindoles from Atropisomeric N‐Aryl Oxindole Derivatives

“…Other transformations using ortho ‐monosubstituted N ‐aryl oxindoles : Having found a promising oxindole system bearing an ortho ‐monosubstituted aryl group, we moved to investigate the construction of a quaternary carbon center at C3 in the oxindole scaffold by alkylation or cycloaddition. Alkylation of oxindole 16 with an aqueous solution of NaOH and excess MeI in the presence of tetrabutylammonium hydrogensulfate provided syn ‐ 20 a in 70 % yield as a single diastereomer (Table , entry 1) . Allylation and prenylation were also effective to synthesize syn ‐ 20 b and syn ‐ 20 c in moderate to high yields with high diastereoselectivities (entries 2 and 3).…”

“…Alkylation of oxindole 16 with an aqueous solution of NaOH and excess MeI in the presence of tetrabutylammonium hydrogensulfate provided syn-20 a in 70 %y ield as as ingle diastereomer ( Table 4, entry 1). [22] Allylationa nd prenylation were also effective to synthesize syn-20 b and syn-20 c in moderate to high yields with high diastereoselectivities (entries 2a nd 3). The relative stereochemistry of the resulting allylation product syn-20 b was determined by NOESY analysiso fsyn-20 c after conversion by olefin cross metathesis with 2-methyl-2-butene.…”

Structure, Bioactivity and Synthesis of Natural Products with Hexahydropyrrolo[2,3‐b]indole

“…Reaction of 133 with (S)-1-phenylethylamine provided the diastereomeric lactams 157, which were separated, then independently reacted with methylamine and reduced to provide the desired targets. [185] Trost described the earliest examples of molybdenum catalyzed enantioselective allylation of prochiral nucleophiles, reported an interesting route to (À)-esermethole (145) based on this chemistry (Scheme 31). [186] Excellent yields and good-to-excellent enantioselectivities were obtained with a large variety of functionalities at the three positions of the starting oxoindole 146, which provided 3-allyloxoindole (159) with 82 % ee.…”

Enantioselective Synthesis of Quaternary Carbon Stereocenters: Addition of 3‐Substituted Oxindoles to Vinyl Sulfone Catalyzed by Pentanidiums

“…Gratifyingly,byinstalling different halogens to the two benzyl Rg roups on the pentanidium structure,i mprovement in enantioselectivity was achieved and ah igh level of enantiocontrol was obtained with brominated pentanidium 1d or iodinated pentanidium 1e,p roviding 3,3-dialkyl-substituted oxindole 4awith 90 % ee (entries [13][14]. Overall, am oderate level of enantioselectivity was obtained using pentanidium 1a as catalyst (entry 9).…”

“…Overall, am oderate level of enantioselectivity was obtained using pentanidium 1a as catalyst (entry 9). Gratifyingly,byinstalling different halogens to the two benzyl Rg roups on the pentanidium structure,i mprovement in enantioselectivity was achieved and ah igh level of enantiocontrol was obtained with brominated pentanidium 1d or iodinated pentanidium 1e,p roviding 3,3-dialkyl-substituted oxindole 4awith 90 % ee (entries [13][14]. It is noteworthy that pentanidiums with four halogenated benzyl Rg roups would lead to unsatisfactory outcomes in terms of reaction rate and stereocontrol.…”