The asymmetric Friedel-Crafts reaction is one of the most powerful methods to synthesize optically active aromatic compounds, [1] and chiral Brønsted acids have recently emerged as efficient catalysts.[2] Chiral phosphoric acids, first introduced by Akiyama et al. and Terada and Uraguchi as organocatalysts, [3] were shown to be effective in the FriedelCrafts alkylation reactions of indoles and pyrroles by several groups. However, electrophilic partners that can be activated by chiral phosphoric acids in Friedel-Crafts reactions have, so far, been limited to imines, [4] enamides, [5] a,b-unsaturated carbonyls, [6] and nitroolefins. [7] Developing new, suitable electrophilic partners and novel catalytic models for chiral phosphoric acid catalyzed reactions are extremely desirable. In this regard, vinyl ether [8] and nitroso compounds [9] have recently been developed successfully.[10] Alcohols are among the most abundant chemicals and synthetic intermediates, however, their use in enantioselective FriedelCrafts reactions has only appeared recently.[11] To the best of our knowledge, the only example involving the use of alcohols in the Brønsted acid catalyzed asymmetric FriedelCrafts reaction was carried out by Rueping et al., in which chiral N-triflylphosphoramide was used and a moderate enantiomeric excess (ee) value was obtained.[6a]During our recent study on the chiral Brønsted acid catalyzed Friedel-Crafts reaction, we found that a chiral phosphoric acid could catalyze the Friedel-Crafts reaction of indole with 2-formylbiphenyl derivatives. Interestingly, this reaction proceeded through a double Friedel-Crafts alkylation process, [12] providing the 9-(3-indolyl)fluorene derivatives with high ee values (Scheme 1).[13] To the best of our knowledge, despite their significant applications in organic synthesis, [14] this represents the first asymmetric synthesis of fluorene derivatives. More interestingly, the current reaction proceeds with the activation of both carbonyl and hydroxy groups by a chiral phosphoric acid. The enantiocontrol is likely to be made possible through the close proximity of the chiral phosphate counterion to the 3-benzylidene-3H-indolium ion.[15] Herein, we report a tandem double FriedelCrafts reaction of indoles with 2-formylbiphenyls, leading to 9-(3-indolyl)fluorene derivatives with up to 96 % ee.We first examined the reaction between 3',5'-dimethoxybiphenyl-2-carbaldehyde (2 a) and 2-methyl indole (3 a) catalyzed by different, readily available, chiral phosphoric acids.[16] To our delight, reaction of 2 a and 3 a in the presence of (S)-1 (5 mol %) and 5 molecular sieves (MS), in toluene at room temperature, proceeded smoothly to afford fluorene 4 aa in 70 % yield with 75 % ee (Table 1, entry 1). Optimization of the reaction conditions was carried out and the results are summarized in Table 1. Lowering the temperature to 0 8C resulted in an increase of enantioselectivity (81 % ee; Table 1, entry 2). Several solvents, namely, benzene, dichloromethane, and carbon tetrachloride, were scree...