title: Control of extremely fast competitive consecutive reactions using micromixing. Selective Friedel-Crafts aminoalkylation.
abstract: Friedel-Crafts reactions of aromatic and heteroaromatic compounds with an N-acyliminium ion pool were studied. The reaction of 1,3,5-trimethylbenzene in a batch reactor gave rise to the selective formation of a monoalkylation product (69%). Presumably, the second alkylation is slower than the first alkylation because of the protonation of the monoalkylation product that decreases its reactivity. The reaction of 1,3,5-trimethoxybenzene, however, gave rise to the formation of both monoalkylation (37%) and dialkylation (32%) products. Disguised chemical selectivity due to faster reaction than mixing seems to be responsible for the lack of selectivity. The use of micromixing was found to be quite effective to solve this problem to increase the selectivity. The monoalkylation product was obtained in 92% yield together with a small amount of the dialkylation product (4%). The reaction with various aromatic and heteroaromatic compounds revealed that the low mono/dialkylation selectivity was observed only for highly reactive aromatics. In such cases, the use of micromixing was quite effective to improve the selectivity. On the basis of micromixing, the selective sequential dialkylation using two different N-acyliminium ions was achieved. CFD simulations using a laminar flow and finite-rate model are consistent with the experimental observations and clearly indicate the importance of mixing.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto 615-8510.
authors.forename: Aiichiro
authors.initials: A
authors.lastname: Nagaki
authors.forename: Manabu
authors.initials: M
authors.lastname: Togai
authors.forename: Seiji
authors.initials: S
authors.lastname: Suga
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Aoki
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mae
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Yoshida
mesh_terms: D000478:Alkylation; D018360:Crystallography, X-Ray; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods; D044085:Microfluidics / Q000295:instrumentation / Q000379:methods*; D008958:Models, Molecular; D015394:Molecular Structure; D013816:Thermodynamics
chemical_list: D006841:Hydrocarbons, Aromatic