Compounds reaction with aldehydes

N-Sulphinylamines react with a variety of unsaturated compounds. Reaction with aldehydes appears to proceed via an adduct (166), which... 

Cycloaddition of COj with the dimethyl-substituted methylenecyclopropane 75 proceeds smoothly above 100 °C under pressure, yielding the five-membered ring lactone 76. The regiocheraistry of this reaction is different from that of above-mentioned diphenyl-substituted methylenecyclopropanes 66 and 67[61], This allylic lactone 76 is another source of trimethylenemethane when it is treated with Pd(0) catalyst coordinated by dppe in refluxing toluene to generate 77, and its reaction with aldehydes or ketones affords the 3-methylenetetrahy-drofuran derivative 78 as expected for this intermediate. Also, the lactone 76 reacts with a, /3-unsaturated carbonyl compounds. The reaction of coumarin (79) with 76 to give the chroman-2-one derivative 80 is an example[62]. 

Organohthium and organomagnesium compounds find their chief use m the prepa ration of alcohols by reaction with aldehydes and ketones Before discussing these reac tions let us first examine the reactions of these organometallic compounds with proton donors... 

These compounds are sources of the nucleophilic anion RC=C and their reaction with primary alkyl halides provides an effective synthesis of alkynes (Section 9 6) The nucleophilicity of acetylide anions is also evident m their reactions with aldehydes and ketones which are entirely analogous to those of Grignard and organolithium reagents... 

The addition of isocyanides and azide to aldehyde-derived enamines has led to tetrazoles (533,536). On the other hand the vinylogous amide of acetoacetic ester and related compounds reacted with aldehydes, isocyanides and acids to give a-acylaminoamides (534). Iminopyrrolidones and imino-thiopyrrolidones were obtained from the addition of cyclohexylisocyanide and isocyanates or isothiocyanates to enamines (535). An interesting method for the formation of organophosphorus compounds is found in the reactions of imonium salts with dialkylphosphites (536). 

A -Chloromethylamine attacks ketones in alkaline solution with formation of oxaziranes with cyclohexanone, compound 17 is produced in 50% yield. The reaction with aldehydes with zV-chloromethyl-amine yields predominantly acid amides. However, oxaziranes are also produced here as by-products. From benzaldehyde and A -chloro-methylamine, 2-raethyl-3-phenyloxazirane (15) was obtained in 10% yield. 

Hetero-substituted 2-alkenyllithium compounds, however, show useful levels of regio- and stereoselectivity in reactions with aldehydes, in particular if the cation is held at one terminus of the allylie system by electron-withdrawing or chelating groups. 

These reagents are not isolated but are used directly in reactions with aldehydes, after generation of ate complexes via the addition of an alkyllithium reagent or pyridine11. 2-(2-Propenyl)-1,3,2-dioxaborolane is also metalated upon treatment with lithium tetramethylpiperidide, but mixtures of a- and y-substitution products are obtained upon treatment of this anion with alkylating agents20. Consequently, this route to a-substituted allylboron compounds appears to be rather limited in scope. 

Double deprotonation of tetrahydro-2-(2-nilroethoxy)-2//-pyran (8) and reaction with electrophiles provides a variety of substituted and functionalized nitroaldols1 Reaction with aldehydes affords 2-nitro-l,3-alkanediols 9 in 44 90% yield and high diastereoselectivities. From analogy of their II-NMR spectra and comparison with known compounds, the (R, R ) relative configuration is likely15. 

In the condensation reaction between chloro- and bromo-methyl aryl sulfones and carbonyl compounds, a-sulfonyloxiranes were obtained. In this condensation reaction, bases such as potassium t-butoxides372, NaH373 and aqueous concentrated hydroxide with benzyltriethylammonium chloride under two-phase condensation were used374. In the reaction with aldehydes only the trans-epoxide isomers resulted, whereas lith-iofluoromethyl phenyl sulfone 289375 and 291376 were found to add to aldehydes affording /J-hydroxysulfones 290 and 292, respectively. 

Reactions of Allylic Trialkylstannnanes. Allylic organotin compounds are not sufficiently reactive to add directly to aldehydes or ketones, although reactions with aldehydes do occur with heating. 

The cyclopropylphosphonate anion undergoes the stereoselective addition reaction with aldehydes [106]. Although the Wittig-Horner elimination is not observed at this stage, the olefinic compounds are produced by treatment of the adduct alcohols 201 with NaH in the presence of 18-crown-6 as illustrated in Scheme 76. 

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