Rearrangement ketone/aldehyde compounds

The 1,1-disubstituted epoxide (100 equation 40) undergoes ring expansion rather than hydride migration, to afford materials such as (101) and related products. It is conceivable that an aldehyde was generated in this instance, which then rearranged to the isolated products. This kind of behavior is seen with (102 equation 41) which upon brief treatment with BF3 afforded aldehyde (103) and ketone (104) in nearly equal amounts. When resubjected to the reaction conditions the aldehyde (103) gave a new ketone (105). Compound (103) was used as a precursor to the hydrocarbon cuparene, which has the structure of (103) modified by reduction of CHO to Me in spite of the modest yield, this proved a convenient approach to a structure with two adjacent quaternary carbons. ... 

The Lewis-acid catalyzed rearrangement of epoxides to carbonyl compounds has been studied and it has been found that either ketones or aldehydes can be selectively obtained by the proper selection of reaction conditions. For example, spiroepoxide 81 undergoes rearrangement to aldehyde 82 upon treatment with methylaluminum fcw(4-bromo-2,6-di-tert-butylphenoxide), or MABR, whereas ketone 83 is formed predominantly when antimony pentafluoride is used [94TET3663]. 

The biosynthesis of the T. proceeds according to the isoprene rule . Acyclic hydrocarbons formed in this way can be converted to a multitude of compounds by substitution, oxidation, cyclization, rearrangement, etc. reactions accordingly a large number of T. (>40000 have been described to date) occurs in nature. Included among the T. are not only the hydrocarbons but also the alcohols, ketones, aldehydes, and esters (alternative name terpenoids) derived from them. For nomenclature and technical use of T., see the individual entries and Lit.. ... 

The Ugi reaction is a multi-component organic chemistry reaction (Scheme 7.12), which includes the participation of either a ketone or an aldehyde, an amine, an isocyanide, and a carboxylic acid to form a bis-amide [50]. The particular case shown in Scheme 7.12 corresponds to the study carried out by Buet al. [51]. First, the imine formation is carried out by the reaction between the aldehyde compounds and the amine. Then, the carbon atom of the synthesized imine is attacked by the nucleophilic carbon atom of the isocianide, which yields an adduct as reaction product. In other pathway, the oxygen atom of a carboxylic acid is added to the previous product, and a new adduct is obtained. After an internal rearrangement of the latter molecular structure, a diamide compound is obtained. It is known that for a successful reaction a pH of 3.6 should be used in the reaction media [52]. This important reaction has been often used to prepare hydrophobically modified alginates [52,53]. 

The above processes constitute the first step of the reaction. They residt in rearrangement or decomposition secondary reactions forming acid, ketone, or aldehyde compounds. The ozonization reaction of double bonds is much faster and gives rise to ozonides which also decompose and yield many secondary products. In the case of aromatic rings instable triozonides are obtained and they decompose very quickly... 

Reductions - For unsaturated compounds containing oxygen (allylic alcohols and ethers, ynols, epoxides, a,6-unsaturated ketones, aldehydes, acids and epoxides) nidkel boride (prepared from N1 acetate and NaBH ) selectively and quantitatively hydrogenates the C-C double bonds without rearrangements, hydrogenolysis or carbonyl reductions. 

In an attempt to establish the limits for ODPM reactivity of P,y-unsaturated aldehydes, we have extended our studies to aldehydes 57a,b,c,d, which are monosubstituted at C2. The large number of studies carried out in the di-7t-methane area have established that disubstitution at the central carbon of acyclic 1,4-unsaturated substrates is an important structural requirement for efficient rearrangement. In fact, compounds 2 and 58-" are the only acyclic P,y-unsaturated ketones monosubstituted at C2 that undergo the ODPM rearrangement. 

A-Substituted pyrroles, furans and dialkylthiophenes undergo photosensitized [2 + 2] cycloaddition reactions with carbonyl compounds to give oxetanes. This is illustrated by the addition of furan and benzophenone to give the oxetane (138). The photochemical reaction of pyrroles with aliphatic aldehydes and ketones results in the regiospecific formation of 3-(l-hydroxyalkyl)pyrroles (e.g. 139). The intermediate oxetane undergoes rearrangement under the reaction conditions (79JOC2949). 

From the addition reaetions of acrolein- to aldehyde-derived enamines, aminotetrahydropyrans have been obtained. On heating, these products rearranged to enaminoaldehydes in examples where the initial enamine was disubstituted (320,321). The addition of acrolein to ketone derived enamines has been applied to syntheses of heterocyclic and bridged bieyclic compounds (301,321-323). 

When X=OH, this conversion of acetylenic alcohols to unsaturated aldehydes or ketones is called the Meyer-Schuster rearrangement The propargyl rearrangement can also go the other way that is, 1-haloalkenes, treated with organocopper compounds, give alkynes. ... 

Reaction of the carbanion of chloromethyl phenyl sulphoxide 409 with carbonyl compounds yields the corresponding 0-hydroxy adducts 410 in 68-79% yield. Each of these compounds appears to be a single isomer (equation 242). Treatment of adducts 410 with dilute potassium hydroxide in methanol at room temperature gives the epoxy sulphoxides 411 (equation 243). The ease of this intramolecular displacement of chloride ion contrasts with a great difficulty in displacing chloride ion from chloromethyl phenyl sulphoxide by external nucleophiles . When chloromethyl methyl sulphoxide 412 is reacted with unsymmetrical ketones in the presence of potassium tcrt-butoxide in tert-butanol oxiranes are directly formed as a mixture of diastereoisomers (equation 244). a-Sulphinyl epoxides 413 rearrange to a-sulphinyl aldehydes 414 or ketones, which can be transformed by elimination of sulphenic acid into a, 8-unsaturated aldehydes or ketones (equation 245). The lithium salts (410a) of a-chloro-/ -hydroxyalkyl... 

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