Dihydroxylation Of Alkenes Promoted By PIFA And Investigation On The Synthesis And Application Of Carbamoyl Benzotriazoles

In the first part, the mechanism of the intramolecular dihydroxylation of alkenes promoted by [Bis(trifluoroacetoxy)iodo]benzene(PIFA) is investigated.1,2-diols motif exists in many biologically active natural products and important synthetic intermediates. Our group has developed the intramolecular dihydroxylation of alkenes using PIFA. The obvious advantage is that the "stop-and-flow" strategy allows us to functionalize polyalkenes readily step-by-step despite the activities of the two C=C bonds. Here, by treatment of ortho-biphenylamide with PIFA, the proposed iminolactone was produced. Protection of the hydoxy in the iminolactone and subsequent acidic hydrolysis afforded γ-lactone, whose spectroscopic data are in agreement with those prepared from L-glutamic acid by the known procedure. Therefore,5-exo cyclization was the most likely pathway for the dihydroxylation. Besides, direct hydrolysis of the iminolactone under acidic conditions can give3-alkyl-5-hydroxymethyl-y-lactone, which has been widely found in natural products and pharmaceutically significant compounds. It should be noted that protection and deprotection can be avoided. Therefore, this method is hopeful to provide facile synthesis of natural products.The second part mainly studies the one-pot synthesis of carbamoyl benzotriazoles (RNHCOBt) and it’s usage as an isocyanate substituent. Isocyanate is an important intermediate in organic synthesis, however, the instability limits it’s application to some extent. BtH has been an ideal auxiliary reagent in organic synthesis and RNHCOBt, the derivative of BtH, showed reasonable stability and activity. However, the available methods for the synthesis of RNHCOBt have a variety of disadvantages. Here we developed an efficient one-pot synthesis of RNHCOBt starting from readily available carboxylic acid under mild conditions. The reaction between amino acid and RNHCOBt has also been investigated. Various amino acids can undergo the N-acylation to give the target products in short time with high yield. It is worth mentioning that there is no need to protect the amino acids. Besides, the BtH could be recovered easily. Therefore, RNHCOBt shows a promising prospect in industrial application as a substituent for isocyanate.