Dialkylaminomethyl Sulfides: An Improved Synthesis.

Abstract

DURING another study, several dialkylaminomethyl alkyl (aryl) sulfides were required. A survey of the literature revealed two significant references on their preparation (1,2). According to these 'reports, the dialkylaminomethyl sulfides are formed in erratic yields. For example, from the reactions of morpholine and formaldehyde with thiophenol and rn-thiocresol, the corresponding morpholinomethyl aryl sulfides were obtained in yields of 33 and 79%, respectively (1 ) . Grillot prepared the dialkylaminomethyl aryl sulfides by combining the reactants a t 20°C. and then holding at 8OoC. for 2 to 3 hours. McLeod and Robinson used somewhat milder conditions to prepare the dialkylaminomethyl alkyl sulfides in yields of 50 to 60% ( 2 ) . Their reactions were at room temperature employing a saturated potassium carbonate solution. The inconsistent yields prompted an investigation of this seemingly simple The method of McLeod implies that the reaction will occur under moderate conditions; however, the use of K?CO1 seemed superfluous. If a basic medium is required, the amine should furnish the necessary basicity even after reaction with formaldehyde. Working on this premise, a series of aminosulfides was prepared. The reaction was carried out by adding the secondary amine to a formaldehyde solution maintained at 25 to 30°C., then the thiol was added while maintaining the same temperature. Excellent yields (85 to 95%) of dialkylaminomethyl sulfides were obtained from both aliphatic and aromatic mercaptans. The reaction can be represented by the equation: