Acetaldehydes hydrazones

Products containing two adjacent stereogenic centers were obtained as mixtures of diastereoisomers that could be separated by column chromatography (dr values. Scheme 6.12). The N,N -dimethyl acetaldehyde hydrazone appeared remarkably... 

By coupling the asymmetric Michael additions of a SAMP or RAMP acetaldehyde hydrazone like those shown in equation (30) with hydrolysis and reduction of the chiral (3-substituted 8-oxopentanoates, Enders was able to prepare chiral 8-lactones with control of stereochemistry at C-3 of the lactone ring. As would be expected based on the results shown above, the enantioselectivity in this overall process was high (90-96%) and good chemical yields were obtained. 

Preparation. This iodide can be prepared in 60% yield by the reaction of ethylidene chloride (Aldrich) with ethyl iodide and aluminum chloride. It can also be prepared by the reaction of acetaldehyde hydrazone with iodine and triethylamine (4, 260). This method is based on the procedure of Pross and Sternhell. ... 

An unusual formation of indoles via a formal Fischer cyclizalion of A-pentafluorophenyl hydrazones 147 was discovered by Brooke. Generally, the Fischer reaction demands the ortto-position be unoccupied. However, in refluxing tetraline, hydrazones 147 were transformed into polyfluoroindoles accompanying with the loss of one ort/tn-fluorine. Hydrazones of acetophenone and cyclohexanone afforded the corresponding indoles 148 and 149 in 12 and 18 % yields respectively. In case of acetaldehyde hydrazone, only a minor amount of parent tetrafluoroindole 132 were isolated. The mechanism of the reaction has not be clarified [57]. 

Reagent A is particularly useful for the treatment of the lower aliphatic aldehydes and ketones which are soluble in water cf. acetaldehyde, p. 342 acetone, p. 346). The Recent is a very dilute solution of the dinitrophenylhydrazine, and therefore is used more to detect the presence of a carbonyl group in a compound than to isolate sufficient of the hydrazone for effective recrystallisation and melting-point determination. 

Special reactions of hydrazides and azides are illustrated by the conversion of the hydrazide (205) into the azide (206) by nitrous acid (60JOC1950) and thence into the urethane (207) by ethanol (64FES(19)105Q) the conversion of the same azide (206) into the N-alkylamide (208) by ethylamine the formation of the hydrazone (209) from acetaldehyde and the hydrazide (205) and the IV-acylation of the hydrazide (205) to give, for example, the formylhydrazide (210) (65FES(20)259). It is evident that there is an isocyanate intermediate between (206) and (207) such compounds have been isolated sometimes, e.g. (211). Several of the above reactions are involved in some Curtius degradations. 

In the discussion of benzylamines, we have met medicinal agents that owe their activity to some particular functionality almost without reference to the structure of the rest of the molecule. The hydrazine group is one such function in that it frequently confers monamine oxidase-inhibiting activity to molecules containing that group. Such agents frequently find use as antidepressants. Thus, reduction of the hydrazone of phenyl-acetaldehyde (84) affords the antidepressant phenelzine (85). Similar treatment of the derivative of phenylacetone (86) gives pheniprazine (87). ... 

Acenaphtheno[l,2-e][l,2,4]triazolo[4,3-h][l,2,4]triazine 747 was prepared (79AP147) by cyclizing 3-hydrazinoacenaphtheno[l,2-e][l,2,4]tria-zine 746 with formic acid. Reaction of 746 with sugars gave the hydrazones, which cyclized with iron(III) chloride to give 748 (93BCJ00). Similarly, the acetaldehyde derivative of 746 was cyclized to 748. The structure of 748 (R = Me) rather than 747 (R = Me) was deduced by unequivocal synthesis of the latter by condensation of acenaphthenequinone with 3,4-diamino[l,2,4]triazole (Scheme 155). 

C4H10O2 534-15-6) see Metolazone acetaldehyde (4-methoxyphenyl)hydrazone (C9H12N2O 13815-71-9) see Indometacin acetaldehyde thiosemicarhazone (C3H7NJS 2302-95-6) see Sulfamethizole acetamide... 

Clerici and Porta reported that phenyl, acetyl and methyl radicals add to the Ca atom of the iminium ion, PhN+Me=CHMe, formed in situ by the titanium-catalyzed condensation of /V-methylanilinc with acetaldehyde to give PhNMeCHMePh, PhNMeCHMeAc, and PhNMeCHMe2 in 80% overall yield.83 Recently, Miyabe and co-workers studied the addition of various alkyl radicals to imine derivatives. Alkyl radicals generated from alkyl iodide and triethylborane were added to imine derivatives such as oxime ethers, hydrazones, and nitrones in an aqueous medium.84 The reaction also proceeds on solid support.85 A-sulfonylimines are also effective under such reaction conditions.86 Indium is also effective as the mediator (Eq. 11.49).87 A tandem radical addition-cyclization reaction of oxime ether and hydrazone was also developed (Eq. 11.50).88 Li and co-workers reported the synthesis of a-amino acid derivatives and amines via the addition of simple alkyl halides to imines and enamides mediated by zinc in water (Eq. 11.51).89 The zinc-mediated radical reaction of the hydrazone bearing a chiral camphorsultam provided the corresponding alkylated products with good diastereoselectivities that can be converted into enantiomerically pure a-amino acids (Eq. 11.52).90... 

No corresponding reactions have been reported with ImCSIm. Attempts to extend the reaction to other aldehyde hydrazones (e.g., acetaldehyde-A /V-dimethylhydrazone) failed.[10]... 

Irradiation of an alcoholic solution of the antitubercular drug isoniazid (261) with a low-pressure mercury lamp by Ninomiya and Yamamoto gave isolated yields of the hydrazone (262, 60%) and the hydrazide (264, 17%). Nicotinic and picolinic acid hydrazides reacted similarly, as did other alcohols. The production of (262) was easily understood since it was known that photolysis of ethanol gave acetaldehyde which would react spontaneously with the... 

Most indoles are synthesized by the Fischer indolization reaction. Here a phenylhydrazine is first reacted with an aldehyde, or ketone, carrying an a-methylene group (not acetaldehyde). The corresponding hydrazone is then treated with an acid, often hydrochloric acid. Ring closure occurs, through a [3,3]-sigmatropic change, and ammonia (as the ammonium cation) is lost (Scheme 7.14). 

In addition to the results described, enantioselective access to 2-phosphino alcohols could be accomplished, too [71]. Starting from a borane-protected a-phosphino aldehyde hydrazone 91 as the key intermediate and available by two different approaches, the enantioselective synthesis of the desired 2-phosphino alcohols 93 could be accomplished. Thus, the electrophilic phosphinylation of aldehyde hydrazones 90 (via route I with the chlorodiphenylphosphine-borane adduct or via route II with chlorophosphines and subsequent phosphorus-boron bond formation) and the alkylation of phosphino acetaldehyde-SAMP hydrazones 92 (route III) was carried out (Scheme 1.1.26). 

An alternative access was achieved by alkylation of the a-diphenylphosphino acetaldehyde SAMP hydrazone 95, yielding the hydrazone products 96 in good yields (60-63%) and good diastereomeric excesses (die = 68-71%) as EjZ mixtures, from which the major diastereomer was separated and purified by preparative HPLC. Ozonolysis and in-situ reduction with the borane-dimethyl sulfide complex of the aldehydes generated gave the air-stable borane-protected 2-diphenylphosphino alcohols 97 in good yields (67-83%). Reaction with DABCO afforded the unprotected 2-phosphino alcohols 98 in very good yields (85-91%) and excellent enantiomeric excesses (ee > 96%) (Scheme 1.1.27). 

An alternative synthesis from the Glaxo patents involves Fnedel-Crafts acylation of the 3-position of the indole intermediate 22 (Scheme 5) Reaction of hydrazine 10 with (phenylthio)acetaldehyde gave hydrazone 20, which was subjected to the Fischer indole reaction to give 3-thiophenylindole 21. It is noteworthy that this Fischer cyclization took place at room temperature because most require heat. Reductive desulfurization of 21 using Raney nickel provided indole 22. Acylation of the 3-position... 

Beil 1.601.(326) [668-70] 2JH.A.Iddles C.E.Jackson, AnalChem 6,454-6(1936) (Precipitation of acetaldehyde as hydrazone using 2,4-dinitrophenylhydrazine as a reagent) 3)Kirk Othmer l(1947),38(Qualitative and quantitative methods of determining acetaldehyde) 4)Jacobs(1949),476—8(Qualitative and quantitative methods of detn 5 Ullmanu 3 0953),11... 

Separation of aldehyde dinitrophenylhydrazines by TLC and column chromatography Excess dinitrophenylhydrazine reagent and the hydrazones of acetone, formaldehyde and acetaldehyde, which occur as contaminants, can be removed prior to preparative TLC by column chromatography. Silicic acid (Merck) columns (3x2.1 cm) may be used with chloroform to elute the aldehyde dinitrophenyl-hydrazones. 

The incorporation of [2-14C]pyruvate and [l-14C]acetate into sugars 17 and 18 was investigated.27 Oxidation of the methyl glycosides of sugar 17 with periodate yielded acetaldehyde from the 1-hydroxyethyl branch. The acetaldehyde (2,4-dinitrophenyl)hydrazone was further oxidized by Kuhn-Roth oxidation to acetic acid, which was degraded by the Schmidt reaction to methylamine and carbon dioxide. Periodate oxidation of the methyl glycosides of sugar 18 produced acetic acid from the C-acetyl branch. The acetic acid was isolated, and purified as 1-acetamidonaphthalene. 

The anions of hindered hydrazones allow the introduction of electrophiles at the a-position, thus functioning as acyl anion equivalents after isomerization back to a hydrazone and hydrolysis.For example, the r-butylhydrazone of acetaldehyde gives phenylacetone following the sequence of reactions shown in equation 44. 

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