Iodides reactions with carbonyl compounds

Reaction of a-phenylsulfinyl acetate or ethyl a-(t-butylsulfmyl)acetate with one equivalent of ethylmagnesium bromide or iodide was shown to give the corresponding Grignard reagent 129 or 132, which upon reaction with carbonyl compounds afforded the corresponding adducts. Thus Nokami and coworkers prepared ethyl / -hydroxycarboxylates 130167, jS-keto esters 131168, a,/J-unsaturated esters 133169 and other derivatives by this method. 

The reactions of 2-iodopyrazine, 2-methylsulfanyl-4-iodopyrimidine and 3-iodo-6-phenylpyridazine with lithium tributylmagnesate resulted in very efficient iodine-magnesium exchange to yield the corresponding heteroarylmagnesium species (equations 35-37)" °. The reactions with carbonyl compounds and diphenyl disulfide proceeded with good yields. The reactions proceeded smoothly, and neither the starting iodide nor any butylated compounds derived from nucleophilic addition to the heteroaromatic nuclei were observed. 

Phenylytterbium iodide, C6H5YbI. This reagent can be prepared by reaction of C6H5I with Yb powder in THF. In reactions with carbonyl compounds, it behaves in the same way as Grignard reagents, except that it reacts more readily with esters than with ketones.12... 

Pentadiene-l,5-diols. Alkynylepoxides undergo reductive ring opening to generate allenylsamarium iodides, which, on reaction with carbonyl compounds, deliver the unusual products. 

A few Pd(0)-catalyzed reactions of aUyUc carbonates cannot be classified under Sects. A-O. Cationic Tj -allylpalladium complexes can be reduced by tin(II) chloride to afford a tin-allyl intermediate provided with nucleophilic reactivity (umpolung), which reacts with carbonyl groups (Scheme 62). Tm(II) chloride has been used by Masuyama and co-workers in Pd(0)-catalyzed reduction of aUylic carbonates,allylic cyclic carbon-ates, and even allylic alcohols,followed by reaction with carbonyl compounds. Related results with cyclic carbonates have been reported by Kang and co-workers Diethylzinc and samarium(II) iodide have been used as the reducing reagent. Protona-tion of the allylsamarium intermediate gives overall reduction of the C—O into C—H bond.f ... 

Samarium(II) iodide also allows the reductive coupling of sulfur-substituted aromatic lactams such as 7-166 with carbonyl compounds to afford a-hydroxyalkylated lactams 7-167 with a high anti-selectivity [74]. The substituted lactams can easily be prepared from imides 7-165. The reaction is initiated by a reductive desulfuration with samarium(ll) iodide to give a radical, which can be intercepted by the added aldehyde to give the desired products 7-167. Ketones can be used as the carbonyl moiety instead of aldehydes, with good - albeit slightly lower - yields. 

An interesting novel coupling reaction of allenes with carbonyl compounds mediated by a lanthanide metal species was reported recently [80], The samarium(II) iodide-mediated reaction of various ketones or aldehydes 153 with methoxyallene (56) afforded exclusively y-addition products 4-hydroxy-l-enol ethers 154 in moderate to good yields with low cis/trans selectivity (Scheme 14.39). 

Allyltin difluoroiodide, formed in situ by the oxidative addition of stannous fluoride to allyl iodide, is found to react with carbonyl compounds to give the corresponding homoallylic alcohols in excellent yields under mild reaction conditions (9). 

Epoxides. The reaction of carbonyl compounds with methylene bromide (iodide) and magnesium amalgam gives methylenic olefins (2, 274) ... 

Yields are normally 50-84% but are lower if the two groups R are secondary alkyl cadmium compounds.360 Aryl and alkyl bromides are more suitable than the iodides for this reaction.361 Alkylcadmiums are usually preferred to alkylzincs because of their less ready reaction with carbonyl groups. The preparation of 1-phenyl-3-eicosanone3 62 from stearoyl chloride and bisphenethyl-cadmium provides an example ... 

AUylation and propargylation reactions. In the presence of the (Ph3P)4Pd catalyst, indium(I) iodide form organoindium(III) reagents with allylic halides and propargylic mesylates that react with carbonyl compounds in various solvents. 

Allylation of carbonyl compounds. The reaction of allyl bromide with carbonyl compounds in the presence of zinc iodide is mediated by germanium(II) iodide. Ketones are less reactive than aldehydes and require an excess of the reagent and longer reaction times. 

Allylation. Amalgamated Sm proi iodide) with carbonyl compounds. Dialh Cyclopropanation The Sm-HgO the Simmons-Smith reaction on allylic 1... 

Allylation. Amalgamated Sm promotes reaction of allyl halides (bromide, iodide) with carbonyl compounds. Diallylation of esters occurs. ... 

We add an investigation of Chinese chemists to this section, although it is not related to carbenoid reagents that we have discussed above. Zhou et al. (1993) studied reactions of dimethyl diazomalonate and ethyl diazoacetate with carbonyl compounds mediated by diorganyl tellurides and catalytic amounts of cuprous iodide (8-69). Dibutyl telluride (8.155) yields the dimethyl l-arylethene-2,2-dicarboxylate 8.157 with 4-chlorobenzaldehyde in 95<7b yield at 100 °C. It is assumed that the reaction passes the telluronium ylide 8.156 as intermediate. If so, the process is clearly different from the carbenoid transformations discussed in this section. The originally diazo-substituted C-atom has nucleophilic character in 8.156 and is not electrophilic, as in 8.104. 

A-homoallylic alcohols were prepared in good yields by allylation of dialdehydes or their acetals with allyl bromide, tin(II) chloride, and potassium iodide in water or water/THF (Eq. 8.46). ° Under ultrason-ication, it was found that SnCU could efficiently mediate the aqueous Barbier reactions between carbonyl compounds and allyl bromide to give the corresponding homoallylic alcohols in high yields without using any Lewis-acid catalyst. 

The reaction of phosphorus ylides with carbonyl compounds as a route to fluoro-olefins is prone to complications (see Vol. 2, p. 46), but excellent yields of olefins are obtained upon dehalogenation of fluoroiodomethyltriphenylphos-phonium iodide with zinc-copper couple, e.g, ... 

Mukaiyama, T. Harada, T. Shoda, S. (1980) An efficient method for the preparation of homo allylic alcohol derivatives by the reaction of allyl iodide with carbonyl compounds in the presence of stannous halide, Chem. Lett., 1507-10. 

Sodium acetylide (prepared from sodium amide) is useful for the condensations with primary alkyl halides. However, secondary, tertiary, and primary halides branched at the second carbon atom are dehydrohalogenated to olefins by the reagent. Iodides react at a faster rate than bromides and the latter faster than chlorides. Chlorides are rarely used. The bromides are more common for preparative reactions. Sodium acetylide can also react with carbonyl compounds to yield acetylenic carbinols. 

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