The first enantioselective cyanoamidation of olefins provides quick access to a variety of 3,3-disubstituted oxindoles. The combination of Pd(dba)2, an optically active phosphoramidite, and N, N-dimethylpropylene urea (DMPU) in decalin were found to be the best conditions.
By using carbophilic Lewis acids, In(OTf)3, NiCl2, and AuCl(PPh3)/AgNTf2, a concise and efficient synthesis of 1,3-disubstituted 1,2-dihydroisoquinolines has been achieved via tandem nucleophilic addition and cyclization of 2-(1-alkynyl)arylaldimines. Addition of proton sources such as water, CF3CH2OH, and 2,6-di-tert-butyl-4-methoxyphenol was essential for the Lewis acid-catalyzed tandem reactions with organometallic reagents. By switching these catalysts, various types of nucleophiles such as allylstannanes, silyl enol ethers, alkenylboronic acids, and active methylene compounds could be introduced at the C1 position of 1,2-dihydroisoquinolines in this transformation. Furthermore, this method proved to be applicable to the synthesis of 1H-isochromene derivatives via the same tandem reaction of 2-(1-alkynyl)arylaldehydes.
Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday A facile, divergent access to highly oxygenated benzocyclobutene derivatives was developed via the regioselective [2 2] cycloaddition of a-alkoxybenzynes and ketene silyl acetals. The cycloadducts could be converted to selectively protected alkoxybenzocyclobutenediones, an attractive class of compounds for the synthesis of polyaromatic compounds. As one possible application, divergent access to a regioisomer pair of sulfonylphthalides for the Hauser approach to polyaromatic compounds is described.
a b s t r a c tThe cyanoamidation of olefins was achieved. When N-(2-vinylphenyl)cyanoformamides were treated with palladium catalyst, intramolecular cyanoamidation took place to give corresponding 3,3-disubstituted oxindoles. P(t-Bu) 3 showed a remarkable effect on this reaction. When it was used with Pd(dba) 2 , the reaction was completed in 15 min at 100 C for many substrates. Furthermore, the enantioselective cyanoamidation was accomplished with Pd(dba) 2 and an optically active phosphoramidite to provide optically active 3,3-disubstituted oxindoles. Manipulation of the resulting oxindoles has been studied.
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