Indolines enantioenriched

Katritzky has published a correction concerning the regioselectivity of the lithiation of indoline lithiocarbamates and dithiolithiocarbamates, which in fact afford the C-3 rather than the presumed C-2 lithio species <97S171>. However, Beak has reported that N-Boc indoline (107) can be metalated selectively at the 2-position with ec-butyllithium (s-BuLi)/(-)-sparteine and the resulting enantioenriched intermediates react readily with electrophiles to provide 2-substituted N-Boc indolines 108 with high enantiomeric ratios (up to 99 1) <97JOC7679>. 

Very recently, You and co-workers [21] have developed an elegant cascade FCA-Mannich process of indolyl enones to afford enantioenriched polycyclic indolines with the use of quinine-derived primary amine 6c as the catalyst (Scheme 9.7). Moreover, a-amino acid-derived 1,2-vicinal diamine 7 was proved to be efficient to catalyze the reaction of 4,7-dihydromdoles with a,p-unsaturated ketones [22]. 

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... 

Spirophosphine (335) has been employed as a catalyst for the intra- and inter-molecular /-addition of nitrogen nucleophiles to alkynoates (336) and allenoates (338) to give enantioenriched pyrrolidines (337), indolines, and /-amino-a, -unsaturated carbonyl derivatives (339) with <95%... 

Enantioenriched indolines are very important compounds, which exist extensively in natural alkaloids or unnatural bioactive compounds. The development of facile methods toward chiral indolines continues to be a challenge for organic chemists. Unprotected indole 106 could be considered as a special enamine in an aromatic system. Inspired by the possible shift between enamine and imine of indole in the presence of strong acid. Sun and Chen et al. envisioned that a direct reduction of indole 106 to indoline 107 by a combined catalysis of Lewis base and Br0nsted acid would be highly possible (Scheme 32.24). Indeed, using the strategy... 

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