Multi-component Reactions For The Synthesis Of Mannich Bases,Benzoxazines And O-?-oxoalkyl Carbamates In The Presence Of TBHP

Mannich bases,benzoxazines and organic carbamates play an important role in pharmaceutical,agrochemical and industrial fields.It is sure that there are many papers on the synthesis of the three types of compounds until now.However,developing new pahtyways that are novel,simple,efficient and environmentally friendly are still needed.This work mainly includes two parts: synthesis of mannich base,benzoxazines and organic carbamates.(1)Study on mannich bases,benzoxazines via oxidative cross coupling of phenylboronic acids,paraformaldehyde and amines was developed.A range of solvents,temperatures,oxidants and oxidants with various dosage were screened during the research.The experimental results show that phenylboronic acids,paraformaldehyde and secondary amines can be converted into mannich bases smoothly in high to excellent yields.However,when using primary amines as reactants,benzoxazines are achieved with the addition of K2CO3.Notably,using benzo[b]thiophen-2-ylboronic acid and thiophen-2-ylboronic acid as the starting materials fail to generate the corresponding phenols but give products4-(benzo[b]thiophen-2-ylmethyl)morpholine and 4-(thiophen-2-ylmethyl)morpholine in the presence or absence of TBHP,respectively.The mechanical research shows that it is a domino reaction including the convertion of phenylboronic acids to phenol and the convertion to the corresponding target products.The methodology has advantages of wide range of substrates and easy operation.Our study provides a new pathway for the synthesis of both mannich bases and benzoxazines.(2)Investigation on organic carbamates by oxidative cross coupling of carbon dioxide with ketones and amines was performed.With TBAI as catalyst and TBHP as oxidant,carbon dioxide with ketones and amines could react smoothly to corresponding organic carbamates.It is noted that when using 3-chloro-1-phenylpropan-1-one as the reactant,corresponding3-oxo-3-phenylprop-1-en-2-yl dimethylcarbamate is achieved,which might be due to the elimination of hydrogen chloride.The use of nontoxic,easily achieved and green carbon dioxide as C1 source makes the methodology much more valuable.This study provides a new,simple,effective and environmental friendly pathway for the synthesis of organic carbamatesand the utilization of carbon dioxide.