Photolysis of dipropyldiazirine and trapping of dipropylcarbene with piperidine

Photolysis (350 nm) of dipropyldiazirine in methylene chloride at 4 degrees C produces a mixture off and Z 3-heptene in 81% yield in an E/Z ratio of 1 .8. Tetrapropylazine was formed in less than 5% yield. Photolysis of diprop yldiazirine in the presence of piperidine leads to the formation of a carbe ne-amine adduct. In the presence of 0.06 M piperidine the yield of adduct i s 48%, the yield of E and Z 3-heptene is 47% and the GZ ratio of 3-heptenes is 1.1. The results show that heptene is formed by three pathways. One pat hway involves dipropylcarbene formed directly from the diazirine, the other pathways are attributed to ionic and photochemical reactions of 4-diazohep tane and to the excited state of the diazirine precursor, Dipropylcarbene c an be easily intercepted with a simple trap. The yield of this process is l imited by the efficiency with which the precursor forms the carbene. (C) 19 99 Elsevier Science Ltd. All rights reserved.