Preparation of linear long chain dialdehydes by hydroformylation of linear α,ω-dienes or ω-vinylaldehyde acetals

Abstract

Linear long chain dialdehydes, a class of valuable intermediates for a wide variety of commercially important products and of interesting cross-linking agents for protein and polysaccharides, can be conveniently prepared by hydroformylation of α,ω-diolefins and protected aldehydes having a terminal olefinic double bond. Thus, 1,5-hexadiene and 1,6-heptadiene were converted in a single oxo-process step into the corresponding linear dialdehydes in very high yields (80–98%), using RhH(CO)(PPh 3) 3/Xantphos (1:3) as the catalytic system at 40–60°C and 20 atm (CO: H 2=1). If more stable monoprotected dialdehydes are needed, they can be obtained in a >90% yield by hydroformylation of ethylene acetals of ω-vinylaldehydes, like 2-(9-decenyl)- and 2-(10-undecenyl)-1,3-dioxolane, catalysed by the above Xantphos–rhodium complex under analogous reaction conditions. This catalytic system showed to be superior to platinum complexes such as PtHCl(PPh 3) 3/SnCl 2·H 2O, which require more drastic reaction conditions (100 atm and 100°C) to ensure yields of linear protected aldehydes ranging from 65 to 86%.