Hydroformylation acyclic diastereoselection

Breit reported a substrate-directed diastereoselective hydroformylation of acyclic methallylic and homomethallylic alcohols protected by 2-(diphenylphosphanyl)benzoyl group (63 and 64) using a P(OPh)3/Rh(acac)(GO)2 system and isolated the corresponding < ///-aldehydes in good diastereoselectivity (Table 11, up to 9614 = They... 

An example is the rhodium catalyzed hydroformylation reaction, which is an industrially important homogenous catalytic process [3]. In contrast, it is amazing that such an important transition-metal catalyzed C/C bond-forming process has been employed only rarely in organic synthesis [4]. Part of the reason stems from the difficulty in controlling stereoselectivity. Even though some recently developed chiral rhodium catalysts allow for enantio- and diastereoselective hydroformylation of certain specific classes of alkenes [5, 6], only little is known about the diastereoselective hydroformylation of acyclic olefins [7, 8]. 

Scheme 3. Design of a catalyst-directing group for the control of diastereoselectivity upon hydroformylation of acyclic methallylic alcohols.

With the aid of the o-DPPB functionality a substrate-directed diastereoselective hydroformylation of methallylic alcohol derivatives could be achieved with high levels of acyclic stereocontrol to provide the syn-aldehydes 6 as the major diastereomers [10]. 

In a related approach, Chercheja and Eilbracht [19] examined cyclic olefins together with acyclic and cyclic ketones (Scheme 5.130). Instead of monoden-tate phosphines as ligands, P(OPh)3 was used for the hydroformylation step. In general, the diastereoselectivities with cyclic substrates and reagents, respectively, were lower than those observed in the reaction of acyclic olefins and aldehydes by the Breit group (compare Scheme 5.129). 

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