ABSTRACT
A practical and straightforward access to pyrazolo[3,4-c]quinolines by molecular sieve mediated dehydrogenative [2 + 2 + 1] heteroannulation of N-(o-alkenylaryl)imines with aryldiazonium salts is described using a sp(3)-hybrid carbon atom as a one-carbon unit. The reaction enables the formation of three new chemical bonds, a C-C bond and two C-N bonds, in a single reaction and features simple operation and excellent functional group tolerance.
ABSTRACT
We describe here a new metal-free route for the synthesis of 3-nitroindoles by the nitrative cyclization of N-aryl imines with tert-butyl nitrite. The radical transformation allows the assembly of the indole framework through oxidative cleavage of multi C-H bonds, a nitration, cyclization and isomerization cascade.
Subject(s)
Imines/chemistry , Indoles/chemistry , Nitrites/chemistry , Cyclization , Indoles/chemical synthesis , Metals , Molecular Structure , Nitro Compounds/chemistryABSTRACT
A new, general method for the synthesis of spiro[4,5]trienones is described by the intramolecular ipso-halocyclization of 4-(p-unsubstituted-aryl)-1-alkynes. In the presence of halide electrophiles, a variety of 4-(p-unsubstituted-aryl)-1-alkynes underwent the intramolecular ipso-halocyclization with water smoothly, affording the corresponding halo-substituted spiro[4,5]trienones in moderate to good yields. The obtained spiro[4,5]trienones can be applied in constructing the azaquaternary tricyclic skeleton via Pd-catalyzed Heck reaction. Notably, the prepared spiro[4,5]trienones and azaquaternary tricycles are of importance in the areas of pharmaceuticals and agrochemicals. The mechanism of the intramolecular ipso-halocyclization reaction is also discussed according to the (18)O-labeling experiments and DFT calculations.
Subject(s)
Alkynes/chemistry , Palladium/chemistry , Spiro Compounds/chemistry , Spiro Compounds/chemical synthesis , Catalysis , Cyclization , Molecular Structure , Quantum TheoryABSTRACT
A new palladium-catalyzed C-H bond activation-annulation-amination tandem method was presented for selectively synthesizing 3-(aminomethylene)-2-oxoindolines. In the presence of Pd(dba)(2), xantphos (L8), AgOAc and Na(2)CO(3), a variety of 3-chloro-2-iodo-N-arylacrylamides underwent the reaction with amides or amines to afford the corresponding 3-(aminomethylene)-2-oxoindolines in moderate to good yields.
Subject(s)
Acrylamide/chemistry , Amines/chemistry , Indoles/chemistry , Indoles/chemical synthesis , Palladium/chemistry , CatalysisABSTRACT
A new, efficient Cu-catalyzed intramolecular C-H oxidation/acylation method has been developed for the synthesis of substituted indoline-2,3-diones (isatins). In the presence of CuCl(2) and O(2), a variety of formyl-N-arylformamides underwent the tandem reaction to afford the corresponding indoline-2,3-diones in moderate to good yields. It is noteworthy that the reaction serves as the first example of transition-metal-catalyzed transformation for the preparation of indoline-2,3-diones.
