The amides of dehydroabietic acid in synthesys of spiropyranes with the participation of carbonyl compounds

Abstract

The abstract presents the synthesis of new spiropyranes from substituted 5-aminoisatin 6 in multicomponent reaction with different carbonyl compounds. It is known that spiropyranes have various activities, which depend from spatial structure and substituents [1]. From the other side, previously mentioned dehydroabietic acid 1 [2] is interesting object to study due to its molecular structure, chemical and biological properties.Initially, our strategy was to obtain the substituted isatine 6 from easily accessible isatine 3. To implement that approach, previously obtained [2] 5-nitroisatine reacted with fivefold excess of ethylene glycol [3] using 10 mol% p-toluenesulfonic acid in boiling toluene to give 4 in good yield. Next, the obtained dioxalane 4 was introduced into the reduction reaction, where the best yield was reached using the fivefold excess of tin (II) chloride [3] as reducing agent. The amidation reaction between 5-aminodioxalane 5 and chloride 2 took place in dry chloroform, using as acceptor the moderate excess Et3N [3]. During the deprotecting essay of dioxalane cycle [3] the best conditions were aqueous acetone (1:3) and 96% sulfuric acid at 350C, leading to desired isatine 6 with 75% yield. The final stage was famous three component reaction [4] between the desired isatine 4, malononitrile and carbonyl compound. The first example [3] started from pyrazoline-2-one, yielded 57% the desired compound 7. Another carbonyl compound – acetoacetic ester gave the compound 8 with 66% yield [3]. But in case of 2,4-pentanedione the reaction haven’t succeeded in different conditions selection (various solvents and long-term boiling).