Diethylamine, aluminum complexes

Other Compounds. Primary and secondary amines add 1,4- to isoprene (75). For example, dimetbylamine in ben2ene reacts with isoprene in the presence of sodium or potassium to form dimetby1(3-metby1-2-buteny1)amine. Similar results are obtained with diethylamine, pyrroHdine, and piperidine. Under the same conditions, aniline and /V-metbylaniline do not react. Isoprene reacts with phenol in the presence of aluminum phenoxide (76) or concentrated phosphoric acid (77) to give complex products. 

Tertiary amine-functionalized olefins are not difficult to polymerize and copolymerize with group IV catalysts, provided that sufficient steric hindrance is present around the nitrogen atom. Amines of sufficient bulkiness, including diisopropyl and diphenyl derivatives, can be polymerized without the necessity of protection by Lewis-acid complexation. Smaller monomers (such as dimethyl and diethylamines) can be polymerized if 1 equiv of a proper alkylaluminum protecting group is used (vide infra). However, if the amine functionality is too near to the double bond, the additional steric bulk provided by the aluminum species may actually inhibit monomer coordination and polymerization. 

Amines are good Lewis bases, donating two electrons to electron-deficient atoms to form a dative bond in the expected ate complex (see Chapter 2, Section 2.5). Diethylamine (iV-ethylethanamine, 40) readily reacts with the strong Lewis acid to form ate complex 41. Note the dative bond between nitrogen and aluminum and the direction of the arrow from the electron-rich nitrogen atom to the electron-deficient aluminum atom. Similarly, tertiary amine 42 (iV-ethyl-iV-methylethanamine) reacts with boron trifiuoride (BF3) to form ate complex 43. Amines will be used as Lewis bases several times in this book. 

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