Acids acid-catalyzed condensation

Acid catalyzed condensation of an alcohol and a carboxylic acid yields an ester and water and IS known as the Fischer esterification... 

Because they are widely used as solvents many simple dialkyl ethers are commercially available Diethyl ether and dibutyl ether for example are prepared by acid catalyzed condensation of the corresponding alcohols as described earlier m Section 15 7... 

Acid catalyzed condensation of alco hols (Sections 15 7 and 16 5) Two... 

An important synthetic process for forming a new carbon—carbon bond is the acid-catalyzed condensation of formaldehyde with olefins (Prins reaction) ... 

Methyl Isopropyl Ketone. Methyl isopropyl ketone [563-80-4] (3-methyl-2-butanone) is a colorless Hquid with a characteristic odor of lower ketones. It can be produced by hydrating isoprene over an acidic catalyst at 200—300°C (150,151) or by acid-catalyzed condensation of methyl ethyl ketone and formaldehyde to 2-methyl-l-buten-3-one, foUowed by hydrogenation to the product (152). Other patented preparations are known (155,156). Methyl isopropyl ketone is used as an intermediate in the production of pharmaceuticals and fragrances (see Perfumes), and as a solvent (157). It is domestically available from Eastman (Longview, Texas) (47). 

The acid catalyzed condensation of benzaldehydes with 2-acetyIpyridine provides access to hydroxy- or amino-indolizines (Scheme 58a) (71CB1629,71CB1645). A remarkable synthesis of fused pyrrolidines in which aldehydes also provide C-2 is exemplified in Scheme 58b... 

The unsaturated tetraoxaquaterene (accompanied by linear condensation products) was first synthesized in 18.5% yield by the acid-catalyzed condensation of furan with acetone in the absence of added lithium salts. Other ketones also condensed with furan to give analogous products in 6-12% yield.A corresponding macrocycle was also prepared in 9% yield from pyrrole and cyclohexanone. The macrocyclic ether products have also been obtained by condensation of short linear condensation products having 2, 3, or 4 furan rings with a carbonyl compound. ... 

In general, fluorinated sulfonic acids can be used as eatalysts for various cationic cyclizations Typical examples are the triflic acid catalysis in the double cyclization of A,VV-dibenzylpropynylamine [82] (equation 30) and the fluorosulfonic acid catalyzed condensation of phenylacetaldehyde [<5J] (equation 31)... 

Cook et al. 45) have studied the structure of the enamines of bicyclic ketones such as norbornanone. Acid-catalyzed condensation of norbornaiie withhexamethylenimineledto a 1 I mixture of the corresponding enamine (87) and its dihydro derivative (88),... 

Muiik and Kim (65) have shown that the acid-catalyzed condensation of desoxybenzoin with morpholine led only to the thermodynamically more stable CIS isomer of the corresponding enamine (128). 

Ibers used the Paal-Knorr furan synthesis to prepare a key intermediate for the synthesis of novel porphyrin-like aromatic macrocycles. Bis yrolyljfuran 27 was available in good yield via the acid catalyzed condensation of diketone 26. ... 

The formation of structure (24) is very difficult to rationalize in terms an acid-catalyzed condensation mechanism, but the formation... 

Under appropriate conditions 1,3-dioxanes can be obtained in moderate to good yields. Below 70 °C the acid-catalyzed condensation of alkenes with aldehydes yields 1,3-dioxanes as major products, while at higher temperatures the hydrolysis of dioxanes to diols is observed. 

Acid catalysts, such as metal oxides and sulfonic acids, generally catalyze condensation polymerizations. However, some condensation polymers form under alkaline conditions. For example, the reaction of formaldehyde with phenol under alkaline conditions produces methy-lolphenols, which further condense to a thermosetting polymer. 

The first cyclopent[A]azepine 19 was obtained as dark-green crystals by the acid-catalyzed condensation of 4-hydroxy-2,3,4-triphenylcyclopent-2-en-l-one (18) with pyrrolidine in refluxing toluene.106... 

Compound 15 is prepared in two steps acid-catalyzed condensation of the pyrimidinediamine with ethyl aceloacelale provides ester 14, which cyclizes under strongly basic conditions. The pyrimidodiazepinone 15 undergoes ring contraction to 7-isopropenyl-7//-purin-8(9//)-one (16) on prolonged heating under basic conditions.297... 

Schemes based on the acid-catalyzed condensation of a bipyrrole with a dipyrrylmethane are in general unsuccessful for the synthesis of corroles. Thus, the bipyrroles 1 fail to give corroles when reacted with the appropriate dipyrrylmethane 2.10,11 However, cobalt(III) corrole 3 can be prepared in moderate yield by a [2 + 2] approach involving bipyrrole T and dipyrrylmethane 2 bearing formyl groups and carboxylic groups, respectively, and heating initial condensation products, presumably norbilenes, with cobalt(II) acetate and triphenylphosphane in methanol.12...

As in the [22]porphyrin(3.1.3.1) series, the cyclohexene moieties being part of the bridges originate from the preparation of the dimers from dimethylpyrrole and a hydronaphthalene diketone by acid-catalyzed condensation. The synthetic approach developed by Franck2b has the advantage over the foregoing method that more stable conventional pyrroles and dipyrryl-methanes can be used to form the macrotetracycle in a stepwise manner. 

The isosmaragdyrins have been prepared1 -14 by a McDonald-type strategy. On acid-catalyzed condensation between an a-unsubstituted terpyrrole 3713 and a dipy rrylmethanedicarbaldehyde 43 the macrocycle 44 is formed directly without the requirement of an oxidation step. In the primarily formed diprotonated form of isosmaragdyrin 44, the cyclic conjugation is disrupted. 

Thus, small amounts of sapphyrins can be obtained via acid-catalyzed condensation between 3,4-dimethylpyrrole-2,5-dicarbaldchydc (51) and 3,4-dimethylpyrrole yielding the de-camethylsapphyrin 52. 

Pentaphyrin(5.5.5.5.5) has not yet been obtained although a synthetic route leading to this type of macrocyclc has been sketched out. It has been observed that on formation of [34]por-phyrin(5.5.5.5) by an acid-catalyzed condensation of an appropriate monopyrrole the corre-... 

Chiral oxazolidines 6, or mixtures with their corresponding imines 7, are obtained in quantitative yield from acid-catalyzed condensation of methyl ketones and ( + )- or ( )-2-amino-l-phcnylpropanol (norephedrine, 5) with azeotropic removal of water. Metalation of these chiral oxazolidines (or their imine mixtures) using lithium diisopropylamide generates lithioazaeno-lates which, upon treatment with tin(II) chloride, are converted to cyclic tin(II) azaenolates. After enantioselective reaction with a variety of aldehydes at 0°C and hydrolysis, ft-hydroxy ketones 8 are obtained in 58-86% op4. 

The conversion of the cyclic hexamer of fiiran and acetone into naphthafiirophane was reported <96TL6201>. Stepwise synthesis of core-modified, zncso-substituted porphyrins (e.g., 19) was achieved by acid catalyzed condensations <96TL197>. 

An important reaction of silicon compounds containing electronegative substituents, such as the halogens or a Group 15 or 16 element, is hydrolysis, which often occurs very readily even with atmospheric moisture. The primary reaction in silicone production is the hydrolysis of halosilanes, usually the readily available chlorosilanes, to give silanols, which then undergo acid-catalyzed condensation with loss of water, as shown in Scheme 1. 

Acid-catalyzed condensation of ketones with furans gives 2,2 -methylene-bisfurans and eventually, if both 2(5)-positions are free, the quaterenes mentioned in Section XI,A.163... 

An important multicomponent transformation for the synthesis of dihydropyrimidines is the Biginelli reaction, which involves the acid-catalyzed condensation... 

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