Synthesis of Highly Substituted Aniline ando-Phenylenediamine Derivatives Containing Various Substitution Patterns

Abstract

The Diels-Alder reactions of a variety of 2H-pyran-2-ones 1 with alkynes 2 yielding highly substituted aniline and o-phenylenediamine derivatives 4 with novel (and in some cases known but very rare and useful) structural patterns are presented. The effect of substituents of both reactants on the reaction rates was investigated. The reactions were carried out under thermal conditions, as well as at high pressures.

Chloranil as an Efficient Oxidant of the Cyclohexadiene Intermediates Formed by a Cycloaddition of Substituted 2H‐Pyran‐2‐ones and Styrenes En Route to the Boscalid Derivatives

“…This is clearly evident from the 1 H NMR spectra of products 5a-g showing singlet signals for 3-H and 6-H, consistent with the smallest coupling constants existing between the 1,4 arranged protons on the benzene rings (J = 0-1 Hz) [11], whereas in the other case two doublets should appear. Furthermore, these findings are also in agreement with our previous results [10,11,22,23] that cycloadditions of unsymmetrically substituted dienophiles with a hydrogen substituent on one side of the multiple bond generally proceed in a regioselective manner, whereas dienophiles containing substituents on both sides of the multiple bond (such as N,N-diethylpropynamine and ethyl but-2-ynoat) yield both regioisomers. In some cases, the regioselectivity was also corroborated by HMBC NMR studies showing the correlation between 5-Me and 6-H groups (that would not appear if the regioselectivity was reversed) [11].…”

Methyl 2-benzamido-4-(3,4-dimethoxyphenyl)-5-methylbenzoate andN-{5-benzoyl-2-[(Z)-2-methoxyethenyl]-4-methylphenyl}benzamide

“…2H-Pyran-2-ones are useful dienes for such transformations (Afarinkia et al, 1992;Woodard & Posner, 1999). During our research we have already investigated a set of Diels-Alder reactions between substituted 2Hpyran-2-ones as dienes and various alkynes as dienophiles (Kranjc et al, 2004). As an intermediate, an oxabicyclo[2.2.2]octadiene system is formed in this reaction, but it has not been isolated so far.…”

A Mechanistic Study of the Lewis Base-Directed Cycloaddition of 2-Pyrones and Alkynylboranes

“…Such limitations are addressed only by the use of very reactive dienophiles such as ynamides, 7 thereby restricting the scope of products that can be generated by this strategy.…”

“…In both cases, similar trends were obtained. Alkyne substrates bearing phenyl-, n butyl-and t butyl-substituents reacted rapidly under mild conditions to give the corresponding functionalised aromatic products 7, 12-19 in good to excellent yields (entries [1][2][3][4][5][6][7][8]. The combination of thiazole-substituted 2-pyrone 20 and TMS-alkyne 11 resulted in a slower reaction and this process was conducted at slightly elevated temperature, resulting in some protodesilylation of the product.…”