Diastereo- and Regioselective Hydroformylation

A control experiment wherein the phosphorous was replaced with a CH group proceeded with no diastereoselechvity and at a significantly reduced rate, thus providing convincing support for the proposed catalyst-directing role of the triarylphosphine group. 

Direchng groups may be used to reverse intrinsic regioselechvity in addition to controlling diastereoselectivity. In this vein it will be noted that regioselective hydroformy-lahon of allylic alcohols favoring the normally disfavored branched aldehyde product 

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