3 июля, 2015 
Malyar Another process patented by BASF is shown in Scheme 4.10. This process uses only isobutylene, formaldehyde and air as reagents; the only by-product is one molar equivalent of water per mole of product
and it gives citral in just four steps, two of which run in parallel. Such elegance not only has intellectual appeal, but is an excellent example of how industrial chemical synthesis should be carried out, producing valuable products efficiently, at low cost and with minimal environmental impact.
The reaction between isobutylene and formaldehyde produces 2- methylbut-l-en-4-ol, isoprenol, which can be isomerized to prenol or oxidized to isoprenal. Two moles of prenol and one of isoprenal are combined to give the ketal, which then eliminates one prenol (recovered and recycled) to give the enol ether. This ether undergoes a Claisen rearrangement to give an aldehyde containing two double bonds that are perfectly placed to undergo the Cope rearrangement to give citral.
Опубликовано в рубрике 