Phosphoric acid derivatives, selective bond

Chiral phosphoric acid analogs as catalysts in the F-C alkylation reaction of indoles with a,(l-unsaturated aromatic enones were also devised [53]. p,y-Unsaturated a-ketoesters were also used as electrophiles in organocatalyzed F-C alkylations of indoles and 2-naphthols. With indoles, chiral acidic N-triflylphos-phoramide was successfully employed (Scheme 35.4) [28], whereas in the presence of 2-naphthols a thiourea-based catalyst showed better capacity to mediate a sequential F-C/cycUzation process, giving naphthopyran scaffolds in moderate yields and selectivities (up to 90% ee) [54]. Recently, a,P-unsaturated acyl phos-phonates were effectively used as hydrogen bond acceptors for F-C alkylations of indole derivatives in the presence of thiourea catalyst ent-19 [55]. 

N-Boc-protected ethyl trifluoropyruvate imine was effectively used in a F-C reaction with indole derivatives for synthesizing, in high selectivities, quaternary a-amino acids via catalysis with chiral phosphoric acid 26e [64]. A binaphthyl-based chiral sulfonimide [42c] and a chiral squaramide-based hydrogen bond donor [42a] were used as effective catalysts for promoting F-C reaction of indoles with imines. Recently, the F-C alkylation of arenes with glyoxylate imine was described via a chiral phosphoric add (Scheme 35.11) [34]. 

---