Hydroformylation is one of the most important homogeneously catalyzed reactions on an industrial scale. The manufacture of bulk chemicals clearly dominates. Large cobalt- and rhodium-based processes are mature technologies that have been developed over the past 80 years. Meanwhile, the potential of hydroformylation for the production of fine chemicals (perfumes, pharmaceuticals) has also been recognized. This review gives insight into the state-of-the-art of the reaction and its development. It commences with some remarks on the accidental discovery by the German chemist Otto Roelen within the historical and personal framework of the Fischer–Tropsch process, followed by the mechanistic basics of the catalytic cycle, metals used for the catalyst as well as their organic ligands. In addition, the stability of ligands and catalysts is addressed. The huge potential of this transformation is demonstrated using a variety of substrates. Finally, the use of some surrogates for syngas is discussed.

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A series of ribofuranosyl-and 2-deoxyribofuranosyl homo-and spacered-C-nucleosides have been synthesized by reaction of fully protected 3-(1-deoxy-β-D-ribofuranosyl-1-yl)propanal (1), 3-(1,2-dideoxy-β-D-ribofuranos-1-yl)propanal (14), 1-(1-desoxy-β-D-ribofuranos-1-yl)pent-4-yn-3-on (19), 1-(1-desoxy-β-D-ribofuranos-1-yl)-5-phenyl-pent-4-yn-3-on (20), 1-(1,2-didesoxy-β-D-ribofuranos-1-yl)pent-4-yn-3-on (29), and 1-(1,2-didesoxy-β-D-ribofuranos-1-yl)-5-phenylpent-4-yn-3-on (30) with different nucleophiles. The preparation of 1 and 14 proceeds by Knoevenagel reaction with malononitrile, cyanoacetamide and 2-cyano-N-(4-methoxyphenyl)acetamide and subsequent cyclization with sulphur to thiophenes 5, 7, 8, 16 and then by cyclization with triethyl orthoformate to give thienopyrimidine 6 and thienopyrimidinone 9, 10, and 17. Treatment of acetylenic ketones 19, 20, 29, and 30 with acetamidinium chloride, benzamidinium chloride, and S-methylisothiouronium sulphate provided the corresponding pyrimidines 21-26, 31, 32. Finally, the use of 4H-1,2,4-triazol-3-amine and 2-aminobenzimidazole as 1,3-N,N'-dinucleophiles afforded the triazolopyrimidines 35, 39 and the pyrimidobenzimidazoles 36, 37, and 40, respectively. Deprotection of a selected number of Cnucleosides was achieved by one or two steps procedure without serious problems. That makes these C-nucleosides promising candidates for the synthesis of monomers suitable for solid phase nucleic acid oligomerization.

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An efficient preparative procedure is described, leading from b-allyl C-glycosides of D-ribofuranose to alcohols by a hydroboration-oxidation procedure. The corresponding aldehydes were obtained by Swern or Dess-Martin oxidation. Alternatively, two of the alcohols were mesylated to gain access to azides and amines. Treatment of the aldehydes with ethynylmagnesium bromide or phenylethynyllithium and consecutive oxidation of the diastereomeric alcohols provided the acetylenic ketones in good to excellent yields. The obtained derivatives serve as important intermediates for the synthesis of various heterocyclic systems.As part of an ongoing research programme that focuses on C-nucleosides, we described recently the first safe, short, and efficient synthetic route to peracetylated b-allyl Cglycosides of D-ribofuranose and 2-deoxy-D-ribofuranose. At present, the best pathway to prepare a b-allyl Cglycoside of D-ribofuranose proceeds via the 2,3-O-isopropylidene diacetate 1 1-3 by treatment with allyltrimethylsilane (AllTMS) and zinc bromide in nitromethane as solvent (Scheme 1). 4,5 Here, we report the synthesis of a series of products, for example alcohols, amines, aldehydes, and acetylenic ketones that are potentially useful for the preparation of a broad range of nucleoside analogues. In view of the diverse application of C-nucleosides, we wished to develop a versatile synthetic route to these types of compounds. It was decided to attempt this by applying a hydroboration-oxidation procedure. However, initial investigations showed that the ester group of C-glycoside 2 is not stable enough for such reaction conditions. Thus, the acetyl group was replaced by a tert-butyldimethylsilyl group (TBDMS) and by a tert-butyldiphenylsilyl group (TBDPS), providing compounds 4 and 5, 5 respectively. Deacetylation was simply achieved under Zémplen conditions, furnishing 3 nearly quantitatively. Subsequent transformation of the double bond in the terminal alcohol was realized by hydroboration-oxidation of the olefins 4 and 5 to produce the alcohols 6 and 7 in 72 and 82% yield, respectively. As side-products, the corresponding sec alcohols were observed (<10%), which were easily removed by column chromatography. X-ray diffraction studies of compound 7 (Figure 1) established its structure and confirmed the presence of the tetrahydrofuran ring as well as the b-linkage to the hydroxy alkyl residue, with C-1¢ possessing S-configuration.

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