A-hydroxyalkylated

There is a wide variety of dyes unique to the field of hair coloring. Successive N-alkylation of the nitrophenylenediamines has an additive bathochromic effect on the visible absorption to the extent that violet-blue dyes can be formed. Since the simple A/-alkyl derivatives do not have good dyeing properties, patent activity has concentrated on the superior A/-hydroxyalkyl derivatives of nitrophenylenediamines (29,30), some of which have commercial use (31). Other substituents have been used (32). A series of patents also have been issued on substituted water-soluble azo and anthraquinone dyes bearing quaternary ammonium groups (33). 

Substitution reactions on dialkyl peroxides without concurrent peroxide cleavage have been reported, eg, the nitration of dicumyl peroxide (44), and the chlorination of di-/ fZ-butyl peroxide (77). Bromination by nucleophilic displacement on a-chloro- or a-hydroxyalkyl peroxides with hydrogen bromide produces a-bromoalkyl peroxides (78). 

Polymeric OC-Oxygen-Substituted Peroxides. Polymeric peroxides (3) are formed from the following reactions ketone and aldehydes with hydrogen peroxide, ozonization of unsaturated compounds, and dehydration of a-hydroxyalkyl hydroperoxides consequendy, a variety of polymeric peroxides of this type exist. Polymeric peroxides are generally viscous Hquids or amorphous soHds, are difficult to characterize, and are prone to explosive decomp o sition. 

In one process to produce highly activated cellulose for acetylation, cellulose is treated with NaOH (mercerization) followed by a hydroxyalkylating agent, eg, ethylene oxide or propylene oxide, to give a cellulose hydroxyalkyl ether with a DS of 0.05—0.3 (76). The resulting water-insoluble material is highly reactive to conventional acetic anhydride—sulfuric acid acetylation. 

BAYLIS - HILLMAN Vinyl alkylation Amine catalyzed converelon of acrylates to a-(hydroxyalkyl) acrylates or of vinyl ketones to a-(hydroxyalkyO vinyl ketones. 

Cushny has compared the action of d- and Z-hyoscyamines with that of atropine, and of d-homatropine with that of dZ-homatropine in antagonising the action of pilocarpine, and finds that the order of activity of the first three is in the ratio 1 40 20, and of the second two in the ratio 4 2-5. He drew attention also to the important influence of the acyl radical in the tropeines, which exercises the maximum effect when it is a hydroxyalkyl aromatic residue and is laevorotatory and in illustration of this point gives the following table of relative activities on the basis of capacity to antagnonise pilocarpine in the salivary fistula dog —... 

The enamine-imine tautomerism of the indolenine system gives rise to rearrangement reactions of interest in indole alkaloid chemistry. Thus the synthesis of dihydroburnamicine (625) utilized the rearrangement of an acetoxyindolenine to an a-hydroxyalkyl indole, presumably through an intermediate enamine. Similarly 2,3-dialkyl indoles undergo oxidations to 2-acyl indoles (626-631). 

There are two methods for the introduction of a hydroxyalkyl group at position 5 of the pyrazol-3-one ring. Schmidt and Zimmer converted furanediones 258a-k into arylmethylenepyrazol-3-reaction with hydrazine hydrate or methylhydrazine (83Jmechanism proposed for the reaction involves nucleophilic attack of the hydrazine on the ketone carbonyl, followed by attack on the ester carbonyl and ring opening of the... 

An alkene activated by an electron-withdrawing group—often an acrylic ester 2 is used—can react with an aldehyde or ketone 1 in the presence of catalytic amounts of a tertiary amine, to yield an a-hydroxyalkylated product. This reaction, known as the Baylis-Hillman reaction, leads to the formation of useful multifunctional products, e.g. o -methylene-/3-hydroxy carbonyl compounds 3 with a chiral carbon center and various options for consecutive reactions. 

Intermolecular Schmidt reactions of alkyl azides and hydroxyalkyl azides with cycloketones in the presence of a Lewis acid, lead to formation of iV-alkyl lactams and A-hydroxyalkyl lactams respectively in good yield. The synthesis of chiral lactams by an asymmetric Schmidt reaction has also been reported. ... 

Only few successful reports utilizing the chiral auxiliary approach for the a-hydroxyalkylation of allyllic anions have been made. 

Ceric ions react rapidly with 1,2-diols. There is evidence for chelation of cerium and these complexes are likely intermediates in radical generation10 106 The overall chemistry may be understood in terms of an intermediate alkoxy radical which undergoes p-scission to give a carbonyl compound and a hydroxyalkyl radical (Scheme 3.59). However, it is also possible that there is concerted electron transfer and bond-cleavage. There is little direct data on the chemical nature of the radical in termediates. 

The reaction fails if the decarboxylation produces a radical that is easily oxidized, such as an a-hydroxyalkyl radical.2 In intermediate cases, such as tert-alkyl or a-alkoxyalkyl radicals,2 the yield based on the parent quinono is usually improved by using an excess of persulfate and carboxylic acid to compensate for the loss of radicals due to oxidation (footnote b, Table I). 

The Stiles-Sisti reaction (Scheme 12-17) is an azo coupling reaction in which an a-hydroxyalkyl residue is the electrofugic leaving group (Stiles and Sisti, 1960 Sisti et al., 1962). The reaction is used to prepare aldehydes and ketones (e. g., 2-methoxy-... 

Papageorgiou and Benezra204 treated chiral r-butyl (-)-(S)- and ( + )-(R)-2-(p-tolylsulfinyl)propionate with an aldehyde, then pyrolyzed the mixture and obtained chiral a-(hydroxyalkyl)acrylate in 75% e.e. Similarly, condensation of the anion of ( + )-(R)-3-(p-tolylsulfinyl)propionic acid 159 with aldehydes was found to give the diastereomeric [i-sulfinyl-y-lactones, (+)-(Sc4,Rc5,Ps)-160a and ( + )-( c4,Sc5,l s)-160b in an approximate ratio of 60 40205. 

Hydroperoxides, as optically active oxidizing agents 289-291 Hydrosulphonylation 172 /J-Hydroxyacids 619 a-Hydroxyaldehydes, synthesis of 330 a-Hydroxyalkyl acrylates, chiral 329 j -Hydroxycarboxylic esters, chiral 329 3-Hydroxycycloalkenes, synthesis of 313 Hydroxycyclopentenones, synthesis of 310 -Hydroxyesters 619 synthesis of 616 Hydroxyketones 619, 636 Hydroxymethylation 767 a-Hydroxysulphones, synthesis of 176 / -Hydroxysulphones 638, 639 reactions of 637, 944 electrochemical 1036 synthesis of 636 y-Hydroxysulphones 627 synthesis of 783... 

A biomimetic oxidation with perfluorinated porphyrin complexes [(F20TPP) FeCl] showed high catalytic activity with secondary alcohols with over 97% yield in all cases [144]. Furthermore, this catalyst is able to oxidize a broad range of alcohols under mild conditions with wCPBA as terminal oxidant. Here, an a-hydroxyalkyl radical species is proposed as central intermediate. 

Reaction of optically active a-sulphinyl acetate 298a with prochiral carbonyl compounds proceeds with a high asymmetric induction - , the degree of which depends on the nature of substituents at the carbonyl group (equation 252 Table 22) . The jS-hydroxy sulphoxides 422 formed may be transformed to optically active p-hydroxycarboxylic esters 423 (equation 253) and optically active long-chain lactones 424 99 (equation 254). Corey and coworkers have used this method to introduce a chiral centre at C-3 in their synthesis of maytansin °°, and Papageorgiou and Benezra for the synthesis of chiral a-hydroxyalkyl acrylates 425 ° (equation 255). 

In a similar way, Carreaux and coworkers [53] used 1-oxa-l,3-butadienes 4-155 carrying a boronic acid ester moiety as heterodienes [54], enol ethers and saturated as well as aromatic aldehydes. Thus, reaction of 4-155 and ethyl vinyl ether was carried out for 24 h in the presence of catalytic amounts of the Lewis acid Yb(fod)3 (Scheme 4.33). Without work-up, the mixture was treated with an excess of an aldehyde 4-156 to give the desired a-hydroxyalkyl dihydropyran 4-157. Although this is not a domino reaction, it is nonetheless a simple and useful one-pot procedure. 

Samarium(II) iodide also allows the reductive coupling of sulfur-substituted aromatic lactams such as 7-166 with carbonyl compounds to afford a-hydroxyalkylated lactams 7-167 with a high anti-selectivity [74]. The substituted lactams can easily be prepared from imides 7-165. The reaction is initiated by a reductive desulfuration with samarium(ll) iodide to give a radical, which can be intercepted by the added aldehyde to give the desired products 7-167. Ketones can be used as the carbonyl moiety instead of aldehydes, with good - albeit slightly lower - yields. 

The grem-dibromocyclopropanes 152 bearing a hydroxyalkyl group, prepared by the addition of dibromocarbene to allylic or homoallylic alcohols, undergo an intramolecular reductive carbonylation to the bicyclic lactones 153. bicyclic lactone derived from prenyl alcohol is an important precursor for the synthesis of ris-chrysanthemic acid. (Scheme 54)... 

The interaction of carboxyalkylphosphines with aldehydes belongs to the same type of reactions reported above. The phenyl-(a-hydroxyalkyl)-carboxyalkylphosphine products transform into phosphorus-containing lactones (10) and water [Eq. (8)] [72JPR66 73ZC(13)310]. 

Eq. (72)], and 1,3,2,5-dioxaborataphosphoniarinanes (106) [Eq. (73)] were obtained from phenylphosphine without isolation of a-hydroxyalkyl-phosphines (85IZV2359 86IZV2510 87IZV2118 88IZV159). 

Boryl-borate tautomerism This type of tautomerism is observed for boryloxyalkylphosphines (101), (102) possessing a hydroxyalkyl group and electron-acceptor substituents at the a-carbon atom [Eq. (88)] (851ZV1102 90IZV1133). Mutual transformations take place rapidly and the equivalency of methyne protons in NMR spectra serves as evidence of tautomerism. In the crystalline state these compounds exist in form A. The considerable influence of the nature of the solvent (-4 ppm in DMFA - 10 ppm in C6H6) on the position of the signal in the MP NMR spectrum provides evidence in favor of tautomerism. 

Both ionic forms have the same set of characteristic bands in their IR spectra and thus cannot be identified in solution. The 3IP NMR spectrum contains only one averaged signal. The IR study revealed tautomeric transformations in solution. The characteristic absorption band of the P—H bond and carbonyl group appeared in solution spectra that is possible only on dissociation of the a-hydroxyalkyl fragment, present only in the second tautomeric form. An X-ray single-crystal study showed the compound (128) to be in a cyclic form. 

When examining the mechanism of these reactions, it is necessary to consider ion-complex tautomerism and the fact that reactions can proceed through dissociation of a-hydroxyalkyl fragments to the secondary phosphine and aldehyde. 

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