Carbonyl compounds stereoselective olefination

For many years acyclic stereoselection has been one of the main interests in organic chemistry35. The most studied case is 1,2-induction, usually with a-chiral carbonyl compounds or olefins. 

Allylboron compounds have proven to be an exceedingly useful class of allylmetal reagents for the stereoselective synthesis of homoallylic alcohols via reactions with carbonyl compounds, especially aldehydes1. The reactions of allylboron compounds and aldehydes proceed by way of cyclic transition states with predictable transmission of olefinic stereochemistry to anti (from L-alkene precursors) or syn (from Z-alkene precursors) relationships about the newly formed carbon-carbon bond. This stereochemical feature, classified as simple diastereoselection, is general for Type I allylorganometallicslb. 

By using either one of these photosystems, one-electron (3-activation of a,(3-unsaturated carbonyl compounds produced carbon-centered radical precursors which cyclize efficiently and stereoselectively to tethered activated olefins or carbonyl groups. The 1,2-anti-stereochemistry observed contrasts with the general trend of syn-stereochemistry expected in 5-hexenyl radical cyclizations. Application of this methodology was successfully demonstrated by the stereoselective synthesis of optically pure C-furanoside, starting from L-tartaric acid (Scheme 38) [57,58]. 

Berkessel and Sklorz screened a variety of potential co-ligands for the Mn-tmtacn/H202 catalyzed epoxidation reaction and found that ascorbic acid was the most efficient one. With this activator the authors could oxidize the terminal olefins 1-octene and methyl acrylate with full conversion and yields of 83% and 97%, respectively, employing less than 0.1% of the metal complex (Scheme 86). Furthermore, with E- and Z-l-deuterio-1-octene as substrates, it was shown that the oxygen transfer proceeded stereoselectively with almost complete retention of configuration (94 2%). Besides the epoxidation, also the oxidation of alcohols to carbonyl compounds could be catalyzed by this catalytic system (see also Section in.C). 

Y. Yamamoto, S. G. Pyne, D. Schinzer, B. L. Feringa, J. F. G. A. Jansen, Formation of C-C Bonds by Reactions Involving Olefinic Double Bonds - Addition to a,/3-Unsaturated Carbonyl Compounds (Michael-Type Additions), in Methoden Org. Chem. (Houben-Weyl) 4th ed. 1952, Stereoselective Synthesis (G. Helmchen, R. W. Hoffmann, J. Mulzer, E. Schaumann, Eds.), Vol. E21b, 2041, Georg Thieme Verlag, Stuttgart, 1995. 

A brominated polystyrene is reacted with sodium diphenylphosphan to form the polymeric Wittig reagent. Reaction with a halide and a base form the ylid which reacts with the carbonyl compound to the olefin. Wittig olefination can be made stereoselective (33). The formation of cis-olefins is accomplished in salt-free solu-... 

Like a,/Lunsaturated carbonyl compounds, vinyl silanes and particularly vinylsiloxanes do not dimerise readily and can thus be used in excess to drive selective CM reactions. Pietraszuk et al. [56] have exploited this to couple vinyl-triethoxysilane with a variety of olefin partners in good yield and with high stereoselectivity (Scheme 8) [57]. Given the importance of vinylsiloxanes as nucleophilic components in Pd-catalysed coupling reactions [58], their facile and stereoselective modification by CM is a significant development. 

In reaction (28) y-elimination of LiCl with the formation of an epoxide is obviously faster than P-elimination of Me3SiOLi (Peterson-olefination). Seyferth and his collaborators34) found that this reaction takes place when bis(trimethylsilyl)bromo-methyllithium is reacted with carbonyl compounds, albeit not stereoselectively (Eq. (30)). In contrast, thermal dehydrohalogenation of 1,1-dichloro-l-phenyl-dimethylsilyl-alkanes furnishes Z-olefins only (Eq. (31)) according to the results of Larson et al. 35) ... 

The four-coordinate sqnare planar iron(n) porphyrins discussed above are not only of great valne in heme protein model chemistry, but also in chemical applications, since they undergo a wealth of ligand addition reactions. For example it has been shown that TPPFe complexes are active catalysts for important carbon transfer reactions in organic chemistry and are found to catalyze the stereoselective cyclopropanation of aUcenes, olefin formation from diazoalkanes, and the efficient and selective olefination of aldehydes and other carbonyl compounds. The active species in these carbon transfer reactions are presumably iron porphyrin carbene complexes. " It was also found that ferrous hemin anchored to Ti02 thin films reduce organic halides, which can pose serious health problems and are of considerable environmental concern because of their prevalence in groundwater. ... 

The olefination based upon the reaction of benzothiazolyl- and phenyltetra-zolyl sulfones with carbonyl compounds is widely used in the target-oriented synthesis. In order to illustrate the reaction scope, yields and stereoselectivities, in this section we present selected examples of these reactions. The examples include reactions of saturated sulfones with saturated aldehydes, saturated sulfones with o, j6-unsaturated carbonyl compounds, -unsaturated sulfones with saturated aldehydes, and /l,y-imsaturated sulfones with a, -unsaturated aldehydes. The emphasis is given to recent work. A complete account of earlier applications of the modified Julia reaction has been given in the Blakemore review [98]. 

A. Olefinic compounds Acetylenic compounds Aromatic compounds Carbonyl compounds F/c-Oxygen compounds Nitrogen compounds Sulfur compounds Halogen compounds Other heteroatom compounds Organometallic compounds Stereoselective and Stereospecific Electrooxidation A. Carboxylic acids Acetoxylation Methoxylation Acetamidation... 

Addition of a-silylcarbanions to ketones and subsequent elimination of a silanoale or silanol afford the corresponding olefins (Peterson reaction) (eq (33)) [30]. The use of a-silylcarbanions in olefination of carbonyl compounds offers some advantages over the Wittig reaction that the method can be applied to highly enolizable ketones and both cis and trans isomers are stereoselectively formed depending on the reaction conditions employed for the elimination step (eq (34)) [31]. 

Triorganylbismuthines can mediate such C-C bond forming reactions as shown in Scheme 5.38 in the presence or absence of a transition metal salt. Tributylbismuthine promotes the allylation of carbonyl compounds with allylic bromide [91HAC297] and the olefination of diazo compounds with carbonyl compounds in the presence of catalytic amounts of a copper(I) halide [90TL5897]. A combination of triphenylbismuthine and WCle promotes the metathesis of olefins, while a similar combination with TiC facilitates the stereoselective Diels-Alder reaction of unsaturated esters [76TMC183, 93JOC4783]. 

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