“…A variety of reagents, such as BF 3 -etherate, NaBH 4 , polyphosphoric acid, MgO/POCl 3 , Yb(OTf) 3 , Sc(OTf) 3 , Al 2 O 3 /P 2 O 5 , or AcOH are utilized for this condensation reaction (9). Most recently, this condensation reaction has also been reported to proceed in the presence of CAN, (bromodimethyl) sulfonium bromide, AgNO 3 , NBS, organic acids such as p-nitrobenzoic acid, montmorillonite K10, PPA, 2,4,6-trichloro-1,3,5-triazine (TCT), sulfanilic acid, ZrOCl 2 , MgBr 2 and Ga(OTf) 3 (10-13). …”