In this screencast we will examine a multistep roadmap problem in which we are asked to predict the product of successive reactions. Hence we must get each product right to successfully predict the final product! By employing our strategy of naming the starting material and thinking about the reactivity we should be in good shape. We are starting with diethyl malonate which is a compound that has a methylene CH2 group with greater than normal acidity. The CH2 protons have an acidity of around 12 on the pKa scale. So they are readily deprotonated with base such as sodium ethoxide. In the first step we treat with 1,3-dibromopropane to do an SN2 reaction and form a carbon-carbon bond to give product A. In step 2, we deprotonate the second acidic methylene hydrogen which then does an intramolecular (within the same molecule) displacement of the primary bromide to form the cyclobutane ring product B. We then treat with lithium aluminum hydride to fully reduce both esters to the primary alcohols, product C. When we treat that with HBr, we transform the alcohols to primary bromides via protonation of the hydroxyl group and displacement with bromide anion to give D. We are then treating another molecule of diethyl malonate with our new electrophile product D. This is going to form a spirocyclic cyclobutane diester product E! The last sequence of reactions to form the final product F is common to these malonate dieters. In step one, the esters are saponified (hydrolysis in basic conditions) with sodium hydroxide to the disodium carboxylate. The second step with acid protonates to give the diacid that is subsequently heated to decarboxylate one of the acids. We ultimately end up with the mono acid product F.
