Studies On The Synthesis Of 3-Alkylindoles

The progress in synthesis of 3-alkylindoles from indoles, such as bis(indolyl)methanes, p-indolylketones, P-indolylalcohols, β-indolylnitro-compounds, α-indolylmethylamines, was reviewed in recent years. The methods of synthesis of bis(indolyl)methanes, P-indolylketones and gramine derivatives were improved.Synthesis of bis(indolyl)methanes via electrophilic substitution reactions of indoles with aromatic aldehydes and ketones catalyzed by aminosulfonic acid was carried out in 23-96% yield at 30~38 °C in EtOH aqueous solution under ultrasound irradiation.Silica sulfuric acid catalyzed the Michael addition of indole to a,p-unsaturated ketones under ultrasonic irradiation to afford the corresponding p-indolylketones in 50~85% yields at room temperature. Our procedure is characterized by milder conditions, short reaction time, higher yield.An efficient and practical procedure for the Mannich reaction of secondary amine, formaldehyde and indole or N-methylindole employing zinc chloride is presented. A series of gramine derivatives were obtained in 58-98% yields at room temperature in EtOH by using this method.