Utilization of microwave radiation in the synthesis of HMPAO and MIBI

Full text: One of the main problems in organic synthesis is the long reaction times often required for most common reactions. As for the synthesis of HMPAO bisimine 24 h are required to achieve 60% yield. On the other hand, the two available methods for the synthesis of 2-methyl-allyl-formamide, a precursor of MIBI, vary considerably in the reaction times employed (from 3 to 17 h), to obtain an overall yield of 60-90%. To solve this problem, we have decided to investigate the synthesis of HMPAO and MIBI using microwave radiation. Thus, 2.4 eq of 2.3-butane-dione monoxime and 1 eq of 2.2-dimethyl- 1-3-propanediamine, were mixed with acidic A12O3' using ethanol. The yield resulting, as determined by GC was 52%. In the preparation of MIBI precursor, 1 eq of 2-methyl-allyl-amine HCI and 1 eq of formamide were mixed, without A12O3 and submitted to microwave radiation (60W/5min). The reaction mixture was analysed by GC, indicating an overall yield of 30%. The above data, indicate the successful application of this technique to the problem proposed, however we believe that the overall yield of 2-methyl-allyl-formamide may be improved