One-step transformation

A one-step transformation of the C5-OH in 86 to the 5-(piperid-l-y)- or 5-(morpholin-4-yl) derivatives 168 was carried out by heating with the respective amines 166 in the presence of titanium tetrachloride. Tlie reaction probably involved formation of the unisolable 5-chloro compounds 167 (93JHC11) (Scheme 64). 

Ilias, M. and Saue, T. (2007) An infinite-order two-component relativistic Hamiltonian by a simple one-step transformation. Journal of Chemical Physics, 126, 064102-1-064102-9. 

Determination of the acidic sites through IR spectroscopy of adsorbed CO is a valuable tool for the choice of the support when selective or multifunctional processes are to be set up. This technique allowed to identify a particular kind of silica as the support of choice for the selective hydrogenation of citral to citronellal and sepiolite as a Lewis acid support able to promote the one-step transformation of citral into menthol. 

A convenient one-step transformation of primary and secondary amines into the corresponding unprotected guanidines using 4-bcnzy 1-3,5-dimcthyl-IH-pyrazole-l-... 

This chapter deals with [2 + 2]cycloadditions of various chromophors to an olefinic double bond with formation of a four-membered ring, with reactions proceeding as well in an intermolecular as in an intramolecular pattern. Due to the variety of the starting materials available (ketones, enones, olefins, imines, thioketones, etc.. . .), due to the diversity of products obtained, and last but not least, due to the fact that cyclobutanes and oxetanes are not accessible by such a simple one-step transformation in a non-photo-chemical reaction, the [2+2]photocycloaddition has become equivalent to the (thermal) Diels-Alder reaction in importance as for ring construction in organic synthesis. 

The isomerization of allylic alcohols provides an enol (or enolate) intermediate, which tautomerizes to afford the saturated carbonyl compound (Equation (8)). The isomerization of allylic alcohols to saturated carbonyl compounds is a useful synthetic process with high atom economy, which eliminates conventional two-step sequential oxidation and reduction.25,26 A catalytic one-step transformation, which is equivalent to an internal reduction/oxidation process, is a conceptually attractive strategy due to easy access to allylic alcohols.27-29 A variety of transition metal complexes have been employed for the isomerization of allylic alcohols, as shown below. 

In summary, asymmetric cycloadditions are powerful methods for the synthesis of complex chiral molecules because multiple asymmetric centers can be constructed in one-step transformations. Among them, reactions using chiral catalysts are the most effective and promising, and fruitful results have been reported in asymmetric Diels-Alder reactions. 

The high specificity and stereoselectivity of enzymes, as well as the mild conditions under which they react, make enzyme-catalyzed reactions versatile tools in the synthesis of glycoconjugates. In some instances, an enzymic one-step transformation affords higher yields then the conventional and more-complex chemical synthesis. The application of enzymes in glycopeptide synthesis is under active development for selective deprotection and glycosylation purposes. 

Hiemstra and co-workers reported the first example of an iodine-promoted allenyl N-acyliminium ion cyclization for the total synthesis of (+)-gelsedine, the enantiomer of the naturally occurring (-)-gelsedine [72], Compound 341 was prepared from (S)-malic acid. When 341 was dissolved in formic acid with a large excess of Nal and heated at 85 °C for 18 h, 343 was found to be the major product isolated in 42% yield. The latter was then successfully converted to (+)-gelsedine in a multi-step manner. Other routes without the allene moiety failed to provide the desired stereoisomer. The successful one-step transformation of 341 to 343 was key to the success of this synthesis. 

A-Protected 5-aza-2-oxabicyclo[2.2.1]heptanes and their oxo analogs are usually prepared from 4-hydroxyproline or its derivatives in several steps [57JA185 71JHC53, 71N(L)(230)457, 71T961] however, 75 was obtained in a facile one-step transformation involving intramolecular dehydration... 

The hemiacetal hydroxyl group of the aldopyranosuloses 325 was usually protected in the form of the methyl glycoside by treatment with methyl orthoformate in the presence of a Lewis-acid catalyst.208 Higher yields of the corresponding methyl glycosides could be obtained by treatment of a glycopyranosulose with methyl iodide in the presence of silver oxide.211 One-step transformation of the dihydro-furan derivatives 324 into the methyl glycosides (326, 327) by treatment with methanol and formic or trifluoroacetic acid has been reported.212... 

The most important route is the conversion of pyrimidines into 1,3,5-triazines. The first one-step transformation was effected by Taylor and Jefford (62JA3744) by heating the pyrimidine (179) with benzenesulfonyl chloride in pyridine (equation 106). The reaction may be considered as an example of an abnormal Beckmann rearrangement. The mechanism of the reaction of the 4-aminopyrimidine (180) is probably dependent on the nature of the 2-substituent (180, R). If R is an electron-releasing moiety, pathway B seems more likely (Scheme 109). The 4-hydroxypyrimidine (179 R = OH) behaves similarly. Many 2-cyano-1,3,5-triazines may be synthesized by this method. 

In spite of the structural similarity between the starting material and the desired product, a one-step transformation cannot be achieved. 

The 1,4-naphthoquinone system is not only a good acceptor for stabilized carbanions, as exploited by Kraus and Wu [31, 32] (see Scheme 6), but also for radicals. The angular skeleton of the benzo[fl]anthraquinone system is constructed in an elegant one-step transformation by a manganese (Ill)-induced radical addition of a malonic ester derivative 161 to 1,4-naphthoquinone 40 followed by addition of the newly generated radical to the benzene ring to form 162 (Scheme 41) [111], However, the principle has not yet been used in advanced syntheses of angucyclinones. 

A convenient one-step transformation of primary and secondary amines into the corresponding unprotected guanidines using 4-benzyl-3,5-dimethyl-l/f-pyrazole-l-carboxamidine 90 and its polymer-bound variant were described <06S461>. 1,3-Dipolar cycloaddition of polymer-bound alkynes to azomethine imines generated in situ from N-aminopyridine iodides followed by aromatization of the cycloadducts gave polymer-bound pyrazolopyridines that were released from the resin as carboxylic acids with trifluoroacetic acid or as methyl esters with sodium methoxide <06JCO344>. 

The use of PSRs as described in the earher sections of this chapter has been restricted to one-step transformations. However, a highly interesting application of PSRs was first described by CainelH and colleagues [118] in 1980, and further developed by Parlow [120] and more especially by Ley et al. [121-124]. These groups described the use of several PSRs within one reaction sequence. Reactive species such as oxidants and reducing agents do not react with each other when they are polymer-supported consequently, one-pot transformations that cannot be realized in conventional solution-phase chemistry are possible. 

For the same reason, the synthesis of acrylic acid from propylene must be carried out in two separate reactors, one for the oxidation of propylene to acrolein and one for the oxidation of the aldehyde to acrylic acid. This is due to the fact that the requirements needed for the two steps make the two reactions incompatible. Acidity is needed in the second step, to favour the desorption of acrylic acid and save it from unselective consecutive reaction, while on the other hand, acidity is detrimental for the first reaction, because it favours the transformation of propylene to undesired products. Therefore, the development of a process for the one-step transformation of propane to acrylic acid will be possible when a catalyst is developed which possesses active sites able to perform quickly the complete transformation of adsorbed propane to the acrylic acid, the latter being the only product which finally desorbs into the gas phase. Accordingly, best performances in the oxidation of propane to acrylic acid have been reported to be obtained on heteropolyoxomolybdates (26), which are known to couple tuneable acid and redox properties. In this case, acid properties may facilitate the desorption of acrylic acid. 

In a one-step transformation, 4-benzoyl-6-chloropyridazin-3-amine reacts with /V,/V-dimethyl-acetamide dimethyl acetal as condensation reagent to give 3-chloro-7V,iV-dimethyl-5-phenylpyrido[2,3-c]pyridazin-7-amine (13a) in 63% yield with other acetamide acetals, prepared from V Y V-dirnethylaceLamide dimethyl acetal and the corresponding dialkylamine (see Houben-Weyl, Vol. E5, p 138f), the reaction affords 3-chloro-5-phenylpyrido[2,3-c]pyridazines bearing various dialkylamino substituents at C7.19... 

Since the optimum temperature for the hydrolysis step is usually different than that for fermentation, a "one-step transformation" may not be as efficient as two steps. 

Chen, D.-C., Beckerich, J.-M., and Gaillardin, C., One-step transformation of the dimorphic yeast Yarrowia lipolytica, Appl. Microbiol. Biotechnol. 1997, 48, 232-235. 

The one-step transformation of 2- or 3-(l-hydroxyalkyl)-2,3-dihydrobenzofurans to 2- or 3-acylbenzofurans with A -bromosuccinimide was performed with good yields <97H(45)1657>. The asymmetric reduction of dihydrobenzofuran ketoxime ethers to enantiomerically enriched chiral hydroxylamines with reagents prepared from borane and norephedrine has been investigated <97TA497>. An enzymatic resolution of a 3-hydroxymethylbenzofuran using Candida rugosa lipase provides an enantioselective synthesis of vitamin E related antioxidants <97TA45>. 

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