sulfones with nitro ketals promoted by KF on alumina provides the corresponding adducts which, upon treatment with p-toluenesulfonic acid, generate the corresponding N-alkoxycarbonyl-2,5-disubstituted pyrroles. The latter transformation involves a cascade process including ketal cleavage, ring closure and final aromatization by nitrous acid elimination.
Efficient two-step sequence for the synthesis of 2,5-disubstituted furan derivatives from functionalized nitroalkanes: successive Amberlyst A21- and Amberlyst 15-catalyzed processes
The nitroaldol reaction of ketal-functionalized nitroalkanes with α-oxoaldehydes, promoted by Amberlyst A21, followed by acidic treatment (Amberlyst 15) of the obtained nitroalkanol, leads to the formation of 2,5-disubstituted furans in good yields. The procedure was successfully applied to the total synthesis of 1-benzyl-3-(5′-hydroxymethyl-2′-furyl)-indazole (YC-1), an important pharmaceutical target.
A new simple and efficient synthesis of 6‐nitroindoles, starting from N‐carboxylalkylpyrrole‐2‐carboxaldehydes and protected β‐nitro ketones, has been developed. The method involves two distinct domino processes, respectively performed underflowchemicalconditions and microwave irradiation. 6‐Nitroindoles were produced in good to excellent overall yields.
Reaction of sulfonylindoles with protected β-nitro ketones affords the corresponding 3-(2-nitroalkyl)indoles that, under acidic conditions, undergo a sequence of cascade processes finally leading to unsymmetrical1,4-disubstitutedcarbazoles.