A series of 2,2'-bis[(dialkylphosphino)methyl]biphenyls (alkyl-BISBIs) were synthesized and applied to the tandem hydroformylation-hydrogenation of 1-decene. The alkyl-BISBI ligands with "small" primary alkyl groups such as methyl or n-hexyl groups on the phosphorus atoms provided 1-alkanols selectively, whereas those with larger alkyl groups such as isopropyl or neopentyl groups showed much lower conversion from alkanals to alkanols. Observation of rhodium complexes of the BISBI-type ligands under H(2)/CO atmosphere revealed that the presence of a stable [RhH(CO)(2)(ligand)] species seems to be less favorable for the second step, the hydrogenation of aldehydes.
A wide range of epoxides were efficiently converted to protected aldols by hydroformylation-acetalization using Co 2 (CO) 8 as a catalyst in trimethyl orthoformate. The formylation of terminal epoxides was regioselective for the terminal position, and (S)-1-benzyloxy-2,3-epoxypropane was transformed into (R)-1-benzyloxy-4,4-dimethoxybutan-2-ol with retention of the configuration.The aldol addition is one of the most useful C-C bond forming reaction for the synthesis of b-hydroxy carbonyl compounds, and the extensive work on this subject has been devoted to develop the stereoselective and catalytic variants. 1 In general, a control of the reaction between the different aliphatic aldehydes has been understood to be difficult because of some accompanying problems: (1) each aldehyde possibly reacts as an electrophilic acceptor and a nucleophilic donor to give a mixture of aldol products (b-hydroxyaldehydes), (2) the reaction of an aldol product with an aldehyde monomer or with itself gives the aldehyde trimer or aldol product dimer, respectively, and (3) dehydration of an aldol product yields a,b-unsaturated aldehyde which allows Michael-type reaction. 2 Recent advances have overcome these undesired reactions and demonstrated the catalytic and selective condensation between different aliphatic aldehydes. 3 Transition-metal catalyzed hydroformylation of epoxides is also an effective method to give b-hydroxyaldehydes. 4,5 Similar to the aldol reaction above mentioned, the reactive aldehyde function potentially causes some unwanted side reactions such as dimerization of products or reduction of carbonyl function under the hydroformylation condition (Scheme 1). Accordingly, in order to establish the synthetic utility of epoxide hydroformylation, it is required to protect the functional groups (hydroxy and/or formyl group) in situ. A successful example for protection of hydroxyl group is the rhodium-catalyzed silylformylation of epoxides reported by Murai et al. where HSiR 3 is used instead of H 2 . 6 On the other hand, for the protection of formyl group, Orchin et al. attempted the cobalt-catalyzed hydroformylation of cyclohexene oxide in the presence of ethylene glycol which would have trapped the hydroformylation product as an acetal. 7 However, in fact, ethylene glycol coordinated to the cobalt center to retard the reaction. For the purpose of efficient hydroformylation followed by a transformation into acetal, we focused on transacetalization reaction. The use of orthoformate [HC(OEt) 3 ] or acetal [H 2 C(OMe) 2 ] in combination with acid catalyst such as SnCl 2 or PPTS (pyridinium p-toluenesulfonate) was shown to be effective for the in situ acetalization of a formyl group in the rhodium-catalyzed hydroformylation of olefins. 8 Here, we report the cobaltcatalyzed hydroformylation-acetalization of epoxides by using HC(OMe) 3 . Dimethyl acetals of b-hydroxyaldehydes were obtained as a stable protected monomer form.In this system, acidic HCo(CO) 4 , derived from Co 2 (CO) 8 under the reaction condition, operated not on...
Aldehyde derivatives P 0190An Alternative Route to Protected Aldols: Cobalt-Catalyzed Hydroformylation of Epoxides and in situ Protection of β-Hydroxyaldehydes by HC(OMe)3. -Epoxides are transformed into the target compounds via Co-catalyzed hydroformylation followed by in situ acetalization. The chiral epoxide (VII) reacts with complete retention of configuration. -(NAKANO, K.; KATAYAMA, M.; ISHIHARA, S.; HIYAMA, T.; NOZAKI*, K.; Synlett 2004, 8, Special Issue, 1367-1370; Dep. Chem. Biotechnol., Grad. Sch. Eng., Univ. Tokyo, Hongo, Tokyo 113, Japan; Eng.) -Mais 46-064
129 und 74; entsprechend im Falle s: 104, 86, 77 und 36. Fiir ~x-CHa ergaben sich die analogen Werte 494, 419, 347 und 237 bei i bzw. 220, 219, 175 und 132 bei s. Aus diesen Daten wurden welter die Korrelationszeiten der 13C-Segmentbeweglichkeit und der inneren Rotation yon e~-CHa berechnet. O. Fuchs (Hofheim) Hay, J. N. u. M. Wiles (Centre for Materials Sci., Univ., Birmingham). Die Oberfliichenenergie von
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