RESUMO
An efficient method for the stereoselective synthesis of "all center substituted" polycyclic pyrazoles from alkynyl cyclohexa-2,5-dienones and nonstabilized diazoalkanes via sequential [3 + 2]-cycloaddition/[1,5]-sigmatropic rearrangement and aza-Michael reactions is reported. The developed process is highly regioselective and stereoselective. It employs a wide substrate scope to furnish structurally diverse linear and bridged [4.4.n.0] ring-fused pyrazoles in moderate to good yields. One-pot and gram-scale syntheses and synthetic transformations have also been showcased.
RESUMO
Unlike phosphonium ylides used extensively for CâC bond formation, herein we disclose the direct use of phosphonium salts for site-selective alkylation to p-quinols via a 5-membered betaine-type intermediate. This strategy provides a novel and general approach for the synthesis of α-(m-aminoaryl) esters, amides and ketones under ambient conditions. The reaction proceeds through in situ generation of P-ylide, alkylation and aromatization. Reaction is highly compatible with diverse functional phosphonium salts and amines.
RESUMO
A catalytic [3 + 2]-cycloaddition/Friedel-Crafts alkylative desymmetrization strategy has been developed for the stereoselective construction of linear and bridged polycyclic pyrroles from alkynylcyclohexa-2,5-dienones. This strategy was further explored for the synthesis of 3-arylpyrroles under Brønsted acid catalysis. Reaction is highly chemo-, regio-, and stereoselective and is compatible with wide range of functionalized cyclohexa-2,5-dienones/pyrroles (>51 examples, ≤98% yields). Gram-scale synthesis and synthetic utility of the products have also been demonstrated to showcase the robustness of present method.