Reactions of methoxybenzylidene derivatives of 2,2-dimethyl-1,3-dioxane-4,6-dione and their saturated analogs with certain nucleophilic reagents

Abstract

The reactions of the methoxybenzylidene derivatives of 2,2-dimethyl-1,3-dioxane-4,6-dione and their saturated analogs with potassium hydroxide in methanol, ammonia, and hydrazine hydrate were realized. The 1,2-bis(methoxybenzylidene)hydrazines, amides, and hydrazides of methoxybenzylidenemalonic acid, suitable for use as structural blocks in the synthesis of various structures based on them, were prepared and characterized.The methoxyphenyl substituent is a structural fragment of a large number of pharmaceutical preparations, the best known of which are drugs with a stimulating action on the cardiovascular system [1, 2] and neurotropic activity [3].As starting materials containing the above-mentioned fragment for the synthesis of new compounds, unknown in the literature, we chose the methoxybenzylidene derivatives of 2,2-dimethyl-1,3-dioxane-4,6-dione 3 and their saturated analogs 4. Compounds 3 are the products from the condensation of methoxy-substituted benzaldehydes 1 with 2,2-dimethyl-1,3-dioxane-4,6-dione (isopropylidenemalonate, Meldrum's acid) (2).Methods for the production of the 2,5-(3a), 2,4-(3b), and 3,4,5-(3c) methoxybenzylidene derivatives are known in the literature [4], and the 2,3,4-(3c) and 3,4,5-(3d) methoxy derivatives were obtained by an analogous procedure.The hydrogenation of compounds 3 was conducted with sodium borohydride in methanol at room temperature.In view of the fact that the 1,3-dioxane ring in isopropylidenemalonates readily undergoes decomposition with ring opening in reactions with nucleophilic reagents [5-7] we realized the reactions of compounds 3 and 4 with potassium hydroxide in methanol, ammonia (donors of ammonia: ammonium hydroxide and hexamethyldisilazane), and hydrazine hydrate.

Novel type of carbon‐centered antioxidants arylmethyl Meldrum's acids − inhibit free radicals

“…Compounds 1 a‐d , 1 e , 1 f , 1 g,h , 1 i , 1 k , 1 l , 1 m , 1 o , 1 p , 1 q,r , 1 s , 1 t , 2 , 3 , 4 , and 14 are known and their 1 H NMR spectra correspond to literature.…”

“…The impact of the dissociation of C(α)‐H and phenolic OH cannot be strictly distinguished in case of vanillin and syringaldehyde derivatives 1 e,f , because their pK a values in water are similar: around 7–7.5 for Meldrum's acid derivatives , but pK a values of different polyphenols vary from 7 to 9.39 . The relatively high antiradical activity of compounds 1 o,p containing para ‐dialkylamino group can be explained taking into account their zwitterionic structure − according to X‐ray analysis the compounds exist as zwitterions (at least in solid state ). In such case C(α)‐H is already deprotonated as it is necessary for the first step of SPLET mechanism.…”