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Consecutive Three‐Component Coupling‐Addition Synthesis of β‐Amino Enoates and 3‐Hydroxypyrazoles via Ethyl 3‐Arylpropiolates
Author(s) -
Niedballa Jonas,
Reiss Guido J.,
Müller Thomas J. J.
Publication year - 2020
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202000823
Subject(s) - chemistry , sonogashira coupling , aryl , substituent , conjugate , stereochemistry , palladium , organic chemistry , alkyl , mathematical analysis , mathematics , catalysis
Two consecutive three‐component syntheses furnishing β‐amino enoates or 3‐hydroxypyrazoles based upon the Sonogashira alkynylation of aryl iodides and ethyl propiolate were established in mostly excellent yields. The ethyl 3‐arylpropiolate intermediates are Michael systems which are suited for concatenation with conjugate addition or cyclocondensation giving access to libraries of 21 different β‐amino enoates and 17 different 3‐hydroxypyrazoles. The rotational barrier of β‐pyrrolidino enoates was assessed by studying the coalescence of pyrrolidinyl protons in VT‐NMR spectra of electronically different substituted derivatives showing that the electronic substituent effect on the aryl group does not affect the height of the rotational barrier. This indicates that the substituents are essentially oriented orthogonally to the plane of the β‐pyrrolidino enoates.