Structural studies in alicyclic systems

The crystal structures of exo- (22) and endo- (23) adducts of tetracyclone and cyclopentadiene have been determined and the relative orientations of the four phenyl rings shown to be similar in the two structures. The reactions between hemicyclone and a number of substituted benzoquinones gave a series of Diels-Alder adducts. Photolysis of the adducts gave derivatives of (21) and/or (29) other reactions of the parent compound with various reagents were studied. The X-ray crystal structures of oxetane (29) and cyanohydrin (55) were determined. The reactions of the diene (37) with twenty-two dienophiles have been studied and the stereochemistry of the products have been determined by crystallographic or spectroscopic means. With olefinic dienophiles reaction occurs exclusively by attack on the carbonyl-bearing face of the diene component of (37), whilst other dienophiles (benzyne, azo compounds and acetylenes) exhibit mixed π-facial selectivity. The origin of the mixed stereoselectivities is discussed. The X-ray crystal structures of the diene (62) and four Diels-Alder adducts (87), (90), (101) and (102) are discussed. The Diels-Alder reactions between cyclopentadiene and a number of substituted benzoquinones gave a series of adducts. Reduction of these adducts and reactionwith organometallic reagents were investigated. One- and two-dimensional n.m.r. analyses of selected products are discussed