Organic Chemistry ELEVENTH EDITION Chapter 13 Conjugated Unsaturated Systems Solomons Fryhle Snyder Copyright © 2014 by John Wiley & Sons, Inc. All rights reserved.

1,6 addition of Br 2 to 1,3,5-cyclooctatriene

Top products are kinetic, bottom are thermodynamic

Degree of substitution of product double bond determines thermodynamic stability

Diels-Alder Reaction

Forward Diels-Alder Reaction

Retrosynthetic Analysis of Diels-Alder Product Retrosynthetic analysis involves three steps First redraw the product with pencil and make the notations shown in left structure above Step 1: project double bond to opposite side of 6-membered ring (erase & redraw) Step 2: erase bonds bonds in 6-membered ring attached to new double bond carbons Step 3: double bonds in 6-membered ring attached to original double bond carbons

Stereochemistry of Diels-Alder Reaction This is so difficult to see that even molecular models don’t help To understand this it is necessary to do a careful topology analysis using Newman projections (next slide)

X 1 :Y 2 = axial:axial trans (anti) X 2 :Y 1 = equatorial:equatorial trans (gauche) X 1 :X 2 = axial:equatorial cis (gauche) Y 1 :Y 2 = equatorial:axial cis (gauche) X 2 :ring = equatorial:equatorial (anti) Y 1 :ring = equatorial:equatorial (anti) Y 1 and Y 2 are leftmost groups in the reactants; wind up cis to one another X 1 and X 2 are rightmost groups in the reactants; wind up cis to one another and trans to Y 1, Y 2 Start with X 1 and Y 2 which have to be trans because they are anti in the Newman projections Stereochemical Relationships in Diels-Alder Product Groups