Functional group isomerism

Introduction Nomenclature Isomerism Functional groups Properties and reactions Biochemistry... 

The addition of secondary amines to acetylenes is most applicable to the synthesis of conjugated acyclic enamines (50,171,172). Particularly the addition to acetylenic esters and sulfones has been investigated (173-177) and it appears that an initial trans addition is followed by isomerization to more stable products where the amine and functional group are in a trans orientation (178). Enamines have also been obtained by addition of secondary amines to allenes (179). 

Constitutional isomerism is not limited to alkanes—it occurs widely throughout organic chemistry. Constitutional isomers may have different carbon skeletons (as in isobutane and butane), different functional groups (as in ethanol and dimethyl ether), or different locations of a functional group along the chain (as in isopropylamine and propylamine). Regardless of the reason for the isomerism, constitutional isomers are always different compounds with different properties, but with the same formula. 

The 6-substituted 1,4-dioxocins can be used to prepare other 6-substituted derivatives by simple functional group transformations.4,8,9 Especially interesting is the synthesis of the 4/7-4-oxo-2,3-dihydropyran-2-yl-substituted derivative 16 from l,4-dioxocin-6-carbaldehyde (15) by a cyclocondcnsation with Danishefsky s diene.9 Dehydrogenation of 16 yields 2 which can be isomerized to the corresponding isomeric. sr/i-benzene dioxide 3 (X = 4/f-4-oxopyran-2-yl), which is identical with and proved the structure of the naturally occurring antibiotic LL-Z 1220.10... 

The effective carbon number neff is helpful in characterizing surfactants with an inner functional group. Surfactants with isomeric structures can be compared by means of the hydrophobicity index / [69], which indicates the influence of the effective length of the alkane chain on cM ... 

The HLB numbers decrease with increasing chain length, e.g., from 13.25 for sodium decane 1-sulfonate to 9.45 for the C18 homolog [72]. Typical HLB numbers for positional isomers range from 12.3 for sodium dodecane 1-sulfonate to 13.2 for the more hydrophilic 6 isomer [73]. The HLB numbers of alkanesulfonates are less influenced by the isomeric position of the functional group and by substituents than the cM values [68]. HLB numbers can be correlated with partition coefficients for the distribution of a surfactant between the aqueous and oily phases, which emphasizes that the partition coefficient is dependent on the carbon number [68]. 

In our retro-synthetic analysis, we envisioned the pyrrolidinylethanol side chain could be installed via the Ullmann ether formation or the analogous reachons from the aryl-iodide functional group. The key intermediate 9 (cis) in the Medicinal Chemistry route was not stable under strongly acidic or basic conditions since it was easily isomerized to the thermodynamically more stable trans-isomer 9a via... 

In Section 3.5 on alkene isomerization, it was mentioned that Li and co-workers reported a RuCl2(PPh3)3-catalyzed shuffling of functional groups of allylic alcohols in water (Eq. 3.35).140 Since the reaction proceeds through an enol intermediate, allyl alcohols can thus be considered as enol equivalents.203 This has been developed into an aldol-type reaction by reacting allyl alcohols with aldehyde (Scheme 3.11).204 The presence of In(OAc)3 promoted the aldol reaction with a-vinylbenzyl alcohol and aldehyde.205... 

Ans. In order to be isomeric, two classes of compounds with only one functional group each can be isomeric only if the carbon atoms of the functional group (or attached to the functional group) have the same oxidation number. For example, aldehydes and ketones can be isomers because the carbon atoms of their functional groups have the same oxidation number (0). 

List the pairs of organic functional groups that can be isomeric with each other if the numbers of carbon atoms in their compounds are the same. 

Regioisomers Isomeric compounds related to each other by the juxtaposition of functional groups. 

The Nazarov cyclization of vinyl aryl ketones involves a disruption of the aromaticity, and therefore, the activation barrier is significantly higher than that of the divinyl ketones. Not surprisingly, the Lewis acid-catalyzed protocols [30] resulted only in decomposition to the enone derived from 46,47, and CO. Pleasingly, however, photolysis [31] readily delivered the desired annulation product 48 in 60 % yield. The photo-Nazarov cyclization reaction of aryl vinyl ketones was first reported by Smith and Agosta. Subsequent mechanistic studies by Leitich and Schaffner revealed the reaction mechanism to be a thermal electrocyclization induced by photolytic enone isomerization. The mildness of these reaction conditions and the selective activation of the enone functional group were key to the success of this reaction. 

It should be noted that selective silylation of the carbonyl group bound to the atom, which bears the nitro group, was documented (see products 60 Scheme 3.60, Eq. 3 (152, 214, 215),). It cannot be ruled out that silylation of other a-functionalized AN also affords initially intermediates silylated at the functional group, and that these intermediates rapidly and irreversibly isomerize into the respective thermodynamically preferable silyl nitronates. 

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