Synthesis of Branched α-Olefins via Trimerization and Tetramerization of Ethylene

alpha-Olefins are very important bulk and fine chemicals and their synthesis from ethylene, an abundantly available and inexpensive feedstock, is highly attractive. Unfortunately, the direct or on-purpose synthesis of olefins from ethylene is limited to three examples, 1-butene, 1-hexene, and 1-octene, all having a linear structure. Herein, the direct synthesis of 3-methylenepentane and 4-ethylhex-1-ene, branched trimerization, and tetramerization products of ethylene, respectively, is reported. Different molecular titanium catalysts, all highly active, with a selectivity toward the formation of the branched ethylene trimer or tetramer, the employment of different activators, and different reaction conditions are the key to selective product formation. The long-time stability of selected catalysts employed permits upscaling as demonstrated for the synthesis of 4-ethylhex-1-ene (52 g isolated, TON(ethylene) 10.7 <middle dot> 106). The direct syntheses of 3-methylenepentane and 4-ethylhex-1-ene from ethylene are introduced. The key to the novel ethylene trimerization and tetramerization reactions are molecular titanium catalysts with a high selectivity toward the formation of one or other branched alpha-olefin, different activators, and different reaction conditions employed. image