Chapter 18, Problem 2LGP

Dehydroabietic acid is a natural product isolated from Pinus palustris. It is structurally related to abietic acid, which comes from rosin. The synthesis of dehydroabietic acid (J. Am. Chem. Soc. 1962, 84, 284–292) was accomplished by Gilbert Stork. In the course of this synthesis, Stork discovered his famous enamine reaction.

(a) Write detailed mechanisms for the reactions from 6 to 8 below.

(b) Write detailed mechanisms for all of the reactions from 9 to 11 in Stork’s synthesis of dehydroabietic acid. Note that 11 contains a dithioacetal, which forms similarly to acetals you have already studied (Chapter 16).

(Fleming, I., Selected Organic Synthesis, p. 76. Copyright John Wiley & Sons, Limited. Reproduced with permission.)