Addition of Fluorene to Schiff Bases†

Abstract

Addition of fluorene to N-arylmethylideneanilines under conditions of phase-transfer catalysis gives N-aryl-N-[9H-fluoren-9-yl(aryl)methyl]amines 3a-e.

Rapid C–H Transformation: Addition of Diarylmethanes to Imines in Seconds by Catalytic Use of Base

“…π-Donating groups decreased the yield of addition product ( 4ca ). The acidic hydrocarbon fluorene ( 4ha ) was expectedly added to the imine and in higher yield than previously observed . In terms of the imine, halogenated and meta -alkoxylated substrates provided high yields of addition products ( 4ae , 4ag , 4ah , 4al , 4an , 4ao , 4ap ).…”

“…Generating new C–C bonds by C–H transformation of hydrocarbons is vital to sustainable organic synthesis and combines waste prevention with the economy of steps. − Transforming C­(sp 3 )–H bonds without prior modification is challenging, but a surge of studies on direct activation of benzylic, − benzhydrylic, − and allylic − substrates is noted in recent years. New C–C’ bonds are formed through transition-metal-catalyzed cross-coupling ( i.e.…”

Synthesis of Indolines via Base‐Mediated C−H Activation and Defluorinative C−N Coupling, with no Need for Transition‐Metals

“…Solutions to the problem include the choice of intramolecular reaction paths, a reliance on the presence of directing groups, or the harnessing of variations in the steric hindrance or acidity of C−H bonds [8,9] . An approach with many recent examples relies on the specific activation of allylic [10–17] or benzylic C(sp 3 )−H bonds [18–30] . Catalytic syntheses of indoles have profited from this strategy through recent work of Mao and Walsh et al ., who have obtained indoles by condensation of 2‐fluoro‐1‐methylarenes and nitriles via 1,2‐addition and subsequent cyclization in the presence of the base LiHMDS (lithium hexamethyldisilazide) and a cesium salt additive (Scheme 1a) [20] .…”

“…[8,9] An approach with many recent examples relies on the specific activation of allylic [10][11][12][13][14][15][16][17] or benzylic C(sp 3 )À H bonds. [18][19][20][21][22][23][24][25][26][27][28][29][30] Catalytic syntheses of indoles have profited from this strategy through recent work of Mao and Walsh et al, who have obtained indoles by condensation of 2fluoro-1-methylarenes and nitriles via 1,2-addition and subsequent cyclization in the presence of the base LiHMDS (lithium hexamethyldisilazide) and a cesium salt additive (Scheme 1a). [20] Kang et al have presented a related base-mediated and copper-catalyzed condensation of 2-halogen-1-methylarenes with nitriles (Scheme 1b).…”