Unsaturated aldehydes with organometallic

A bimetallic catalyst can be obtained by the reaction of tetrabutyltin with Rh/Si02 catalyst. The partial hydrogenolysis leads to the Rhs[Sn(n-C4H9)2]/ Si02 surface organometallic complexes, which proved to be fully selective in the hydrogenation of unsaturated aldehydes into the corresponding unsaturated alcohols.318... 

An extension of the Erlenmeyer synthesis is the condensation of acylamino acids with triethyl orthoformate which leads to the ethoxymethylene derivatives (297). These can be hydrolyzed to the corresponding enols, which in turn can be converted into chloromethylene compounds, e.g. (298). The lability of the chlorine atom in this compound (see arrows) can be put to good account reaction with organometallic compounds or with benzene and its derivatives under Friedel-Crafts conditions yields unsaturated lactones (298 aryl or heteroaryl in place of Cl). The method is especially valuable in cases where the aldehyde is not readily available. 

The identity of the metal in an organometallic reagent determines whether it reacts with an 0C,P-unsaturated aldehyde or ketone by 1,2-addition or 1,4-addition. 

These products can be used as synthetic equivalents of a,/3-unsaturated aldehydes in Michael reactions. Thus C6HsSCH=CHCH2Cl can be used as the equivalent of acrolein, CH2 =CHCHO, which normally undergoes 1,2- rather than 1,4-addition with organometallic reagents. An interesting example is the preparation of an intermediate (1) to the pyridine annelation reagent of Danishefsky and Cain. ... 

Zhang J, Zhang Y et al (2006) Coupling of N-heterocycle-fosed enyne aldehydes with g, d-unsaturated Fischer carbene complexes. Organometallics 25 1279-1284... 

In the presence of main group organometallic compounds, ketones are obtained. Carbonylation of allylic ester 382 with alkylzinc reagent afforded the ketone 383 in high yield [149]. Carbonylation of allyl chloride 384 in the presence of tin hydride afforded the -unsaturated aldehyde 385 via hydrogenolysis of acylpalladium intermediate [150]. 

Mechanistically related to the Mukaiyama aldol reaction, the carbonyl ene reaction is the reaction between an alkene bearing an allylic hydrogen and a carbonyl compound, to afford homoallylic alcohols. This reaction is potentially 100% atom efficient, and should be a valuable alternative to the addition of organometallic species to carbonyl substrates. However, the carbonyl ene reaction is of limited substrate scope and works generally well in an intermolecular manner only with activated substrates, typically 1,1-disubstituted alkenes and electron-deficient aldehydes (glyoxylate esters, fluoral, a,p-unsaturated aldehydes, etc.), in the presence of Lewis acids. The first use of chiral catalyst for asymmetric carbonyl ene was presented by Mikami et al. in 1989. ° By using a catalytic amount of titanium complexes prepared in situ from a 1 1 ratio of (rPrO)2titaniumX2 (X = Cl or Br) and optically pure BINOL, the homoallylic alcohols 70a,b were obtained in... 

Thioketene Acetals. Anion (1) reacts with aldehydes and ketones to provide the corresponding thioketene acetals aryl and unsaturated aldehydes and ketones are good substrates for this reaction (eqs 3 and 4). Enolizable alkyl ketones also react to provide thioketene acetals (eq 5). Alternative methods for the preparation of these cyclic thioketene acetals involve the use of phospho-nate derivatives, mixed zinc-titanium organometallic reagents, and iV,iV-dimethyl thioamides. The phosphonate reagents are more nucleophilic than (1) and are superior when competitive deprotonation is a problem. 

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