Substituted alkyl groups general

Reactivity of Five-membered Rings with One Heteroatom 

3-quinodimethane (325). The cycloadduct can then be dehydrogenated to the indole (327) (92CC549). 

The fluoride ion-induced fragmentation of (328) is a mild and efficient way of generating of 

3-dimethylene-2,3-dihydrothiophene (329) (88TL2689). In the presence of A-phenyl maleimide it gives the adduct (330). In the absence of dienophile (329) dimerizes to unstable spiro-compound (331) acting at the same time as diene and dienophile. 

4-dimethylenethiophene (333) has been generated from diazene (332) by either thermolysis or photolysis (310-380 nm). The purple-colored biradical (333) undergoes intramolecular dimerization to (334) at - 78°C (the formation of intermolecular dimers is possible at higher temperatures). However, (333) is quiet stable up to 160 K at frozen glassy solution in 2-methyltetrahydrofuran. 

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Alkyl halides have the general formula RX, where R is an alkyl or substituted alkyl group and X is any halogen atom (F, Cl, Br, or 1). 

Because of the generally greater reactivity of >C=C<, -C=C- and aromatic rings toward OH radical addition, H-atom abstraction from alkyl or substituted alkyl groups in the alk-enes, alkynes, and aromatic compounds is generally of minor importance, and Kwok and Atkinson (1995) set the substituent group factors F(>C=C<), F(-C=C-) and F(-C6H5) equal to unity. 

We shall consider as alkyl halides all compounds of the general formula R—X, where R is any simple alkyl or substituted alkyl group. For example ... 

The primary monohydric (aliphatic) alcohols can be formed by substituting alkyl groups within the hydrocarbon chain by OH moieties able to form hydrogen bonds with a nearby molecule. The general formula of such alcohols is H(CH2) OH, where n is the number of carbon atoms in the... 

Non-enolizable aliphatic ketones are cleaved analogously. For example, pivalamide and isobutane are formed in good yield from hexamethylacetone (2,2,4,4-tetramethyl-3-pentanone). Most unsymmetrically substituted ketones afford the four possible products (2 amides and 2 hydrocarbons), but often in unequal amounts, e.g., pivalamide and 2,2-diethylbutyramide in 5 1 proportions from 4,4-diethyl-2,2-dimethyl-3-hexanone. Hexaalkyl-substituted acetone derivatives containing branched alkyl groups generally do not react. 

Alcohols are organic compounds whose molecules contain a hydroxyl (— OH) group covalently bonded to a saturated carbon atom. Thus if we substitute an —OH for an H in CH4, we get CH3OH, methyl alcohol. The functional group of the alcohols is — OH. The general formula for alcohols is ROH, where R is an allyl or a substituted alkyl group. 

Usually, the reactions are complete within hours and give good conversions (40% -90+%). In general, the larger the alkyl or other substituted alkyl group on the ester, the slower the reaction rate. Heteroatom containing substituents do not have a... 

There remains the case of the reaction of N-alkyl and N-substituted alkyl groups with carbonyl compounds. 1-Methylpyridinium bromide reacts slowly with benzaldehyde in ethanolic piperidine to give a, < , / the carbinol (41 = H). The reaction is fairly general (R = Me, Ar, ArCH2),... 

The scope of this asymmetric HDAR was evaluated under the optimized reaction conditions using o-benzoquinone diimide 268. Since the hemiaminal 270 was not stable enough for further analysis, PCC (pyridinium chlorochromate) oxidation was employed to produce the more stable quinoxalinones 271. As shown in Scheme 2.41, a variety of aldehydes 253 bearing simple linear or branched a-substituted alkyl groups were well tolerated and excellent enantioselectivities were generally obtained. 

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