Gold‐Film‐Catalysed Hydrosilylation of Alkynes by Microwave‐Assisted, Continuous‐Flow Organic Synthesis (MACOS)

Abstract

Thin gold films on the surface of glass capillaries have proven to be highly active catalysts for the rapid hydrosilylation of alkynes that are flowed through the reactor while being heated by microwave irradiation. The films are able to be reused at least five times with no loss of activity and with no detectable levels of gold showing up in the hydrosilylated products.

Supported palladium catalysis using a heteroleptic 2-methylthiomethylpyridine–N,S–donor motif for Mizoroki–Heck and Suzuki–Miyaura coupling, including continuous organic monolith in capillary microscale flow-through mode

“…The product was recrystallised from hot EtOH to give a dark brown solid (1.43 g, 90%). 1 NSO: C,67.50;H,5.66;N,6.06. Found: C,67.54;H,5.62;N,6.11. 3.2.6.…”

“…1 NSO: C,67.50;H,5.66;N,6.06. Found: C,67.54;H,5.62;N,6.11. 3.2.6. 4-(4-Benzyloxy)-2-methylthiomethylpyridine (7) This compound was prepared from 5 (1.50 g, 6.88 mmol) and 4-BnOC 6 H 4 B(OH) 2 (2.35 g, 10.32 mmol) using a similar procedure to that described for 6.…”

Microwave‐Assisted Continuous Flow Organic Synthesis (MACOS)

“…Organ and co-workers used a different alternative. They coated thin metal films on the inner surface of capillaries as immobilized nanometer-sized catalysts and also microwave antenna [70][71][72][73][74][75][76][77]. The continuous flow reactor (Figure 25.15) consisted of a stainless-steel holding/mixing chamber with three or four inlet ports that merge into one or two outlets.…”

“…The methodology was further expanded by the use of other metal films to catalyze different reactions. For instance, capillaries coated with gold films comprising a dense, regular layer of gold particles covered by an irregular amorphous layer are highly active for the flow hydrosilylation of terminal alkynes (94) (Scheme 25.22) [74].…”

Panning for gold in a hot flowing stream

“…The first MACOS transformation that the Au-lined capillaries (i.e., gold-on-gold) were used for was the hydrosilylation of alkynes (19). A formal addition reaction, the process involves a number of discrete steps making the catalytic process moderately complex (vide infra).…”