Microwave-assisted synthesis of new substituted anilides of quinaldic acid

Abstract

In this study a one step method for the preparation of substituted anilides of quinoline-2-carboxylic acid was developed. This efficient innovative approach is based on the direct reaction of an acid or ester with substituted anilines using microwave irradiation. The optimized method was used for the synthesis of a series of eighteen substituted quinoline-2-carboxanilides. The molecular structure of N-(4-bromophenyl)quinoline-2-carboxamide as a model compound was determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group with four molecules within the unit cell and the total structure of the compound can be described as "a slightly screwed boat".

Scheme 1

Standard synthesis of quinoline-2-carbonyl chloride (2) together with 4-chloroquinoline-2-carbonyl chloride (3).

Scheme 2

Optimization process of synthesis of N-(4-bromophenyl)quinoline-2-carboxamide (5c) and N-(4-bromophenyl)naphthalene-2-carboxamide (6) under microwave irradiation.

Scheme 3

Optimized microwave-assisted synthesis of substituted quinoline-2-carboxanilides 5–5c, 9–13c.

Figure 1

Molecular structure (ORTEP 50% probability level) with H-bonding interaction (N(1)-H(1)···N(2) 2.663(3) Å) found in solid state structure. Selected interatomic distances (Ǻ) and angles (°): Br1 C14 1.897(3), C11 N1 1.404(4), N1 C10 1.359(4), C10 C1 1.509(4), C1 N2 1.320(4), N2 C2 1.370(4), O1 C10 1.218(3); C11 N1 C10 127.9(2), N1 C10 O1 125.4(3), N1 C10 C1 113.4(2).

Figure 2

Supramolecular architecture in X, view along the a axis.