Indolines, chiral, formation

An increasing number of examples of ring formation through 1,5-electrocyclization of appropriate carbanions are illustrated in Scheme 27. In the last example the use of a chiral alkoxide (R = menthyl or bornyl) results in the formation of chiral indolines with optical purities ranging from 17 to 31%. 

Furthermore, they also developed an intermolecular enantioselective alkyl Heck-type coupling cascade for the formation of functionalized chiral indolines, pyrroHdines, and an isoquinoline from acyclic y- and 5-alkenylsulfonamides via a formal alkene C—H functionalization process. The carbon radical intermediate which is formed in situ under copper system could be oxidized to an alkene leading to the desired products [60] (Scheme 8.24). 

Scheme 8.24 Intermolecular enantioselective alkyl Heck-type coupling cascade for the formation of functionalized chiral indolines, pyrrolidines.

Copper(II)-catalyzed aminocyclization/amination sequences of sulfonamides 308d leading to 2-aminomethylindolines 311d were also accomplished (Fig. 81). In an asymmetric version a chiral catalyst generated from 30 mol% of Cu(OTf)2 and 37.5 mol% of Ph-BOX ligand 25a induced the formation of 2-(aminomethyl)-indoline 311d in 64% yield and 71% ee [408]. 

Cross-coupling carboamination reactions between allenes and 2-haloaniline derivatives or halogenated allylic amines have also been employed for the generation of substituted indolines, and use of an appropriate chiral catalyst for these transformations leads to formation of enantioenriched products [52]. For example, Larock has described the synthesis of indoline 56 via the Pd-catalyzed reaction of aryl iodide 54... 

The inversion in alcohol has been attributed to the formation of hemiketals. Considering only the non-reacting solvents, the best correlation was established between the ee and the solvent basicity represented by the H-bond acceptor ability (P). Solvent acidity (a) did not play any significant role. The experimental results are validated by theoretical calculations. Palladium(ll) trifluoroacaetate-catalysed AH of 2-substituted 0 3-toluenesulfonamidoalkyl)indoles in the presence of (7 )-H8-BINAP as the chiral ligand and TsOH as the Brpnsted acid yielded chiral 2,3-disubstituted indolines with up to 91% Nitrobenzene is hydrogenated to aniline almost quantitatively with Pd-MCM-41 (g) catalyst in supercritical carbon dioxide. Experimental and DFT studies showed that a stepwise mechanism is operative. ... 

---