2-Aryl-3-hydroxy

The mechanism of the stereoselective syntheses of (K)-3-aryl-5-(hydroxy-methyl)oxazolidinones via the Mannenin reaction of aryl carbamic acid esters with (Jt)-glycidyl butyrate has been explored in detail by Brickner et al. [60]. Namely, N-lithiated carbamate derivatives of anilines are allowed to react with the commercially available (K)-glycidyl butyrate (96-98% enantiomeric excess ee) under appropriate conditions to obtain enantiomerically pure (Jt)-3-aryl-5-(hydroxymethyl)oxazolidinones in 85-99% yields, according the pathways depicted in Scheme 19. 

Die Behandlung mit anionischen Nukleophilen (z. B. Natrium-, Lithiumhydrid, Natriumhydr-oxid, -methanolat, Diethoxycarbonyl-methyl-natrium) in siedenden Toluol liefert ausschlieBlich 3-Aryl-5-hydroxy-l, 2,4-oxadiazole216 ... 

Spectroscopic studies of 3-aryl-5-hydroxy-l-pyridazinyl-pyrazoles have shown they exist as hydroxy tautomers (80MI27), while studies of protonation of 3(2H)-pyridazinone and maleic hydrazide indicate that by changing acidity, several neutral and/or cationic species can be present (79AJC2297). 

A large number of variously 2-, 4-, and 5-substituted thiazoles with alkyl, aryl, hydroxy, methylthio, mercapto, halo, and nitro groups have been analyzed by thin-layer chromatography on silica and alumina by the Stahl s technique (167, 170, 172). Among the many systems recommended for the elution of these compounds are the following ... 

Alkyl-, Alkoxy-, Aryl-, Hydroxy-, substituierte Amino-Reste oder... 

Alkyl-substituted pyridines have been complexed with a wide variety of other boron Lewis acids, BH3, B(OH)3, and BX3, where X is a selection of alkyl, aryl, hydroxy, alkoxy, and aryloxy groups <87JCS(P2)77l). 

A series of substituted 2,2,4,4-tetramethylcyclobutanones in which the substituent is alkyl, aryl, hydroxy, amino, or imino yield on photolysis in methanol or ethanol the corresponding alkoxytetrahydrofuran [Eq. (112)] in addition to a cyclopropane derivative formed by decarbonylation.429 Earlier examples of this process occurring in 7,7-dimethyl[3.2.0]bicyclohept-2-en-6-one430 and in (+)-cyclocam-phanone431 have been reported. In all cases, intramolecular hydrogen abstraction is unfavorable, and a carbene is postulated as the intermediate species. 

The aromatic 2-substituted pyrazole 1-oxides 74 are derived from pyrazoles 89 by appending an oxygen atom to the pyridine type ring nitrogen atom of the pyrazole nucleus. The second nitrogen atom of the pyrazole ring can be attached to an alkyl, aryl, hydroxy, or amino group. 

Bond dissociation data [ 165] indicate that C-C bond cleavage can only occur with appropriate substitution at the carbon centers (alkyl, aryl, hydroxy, siloxy, alkoxy)... 

The following German patents have also been taken out for alipliatic acid mercurials Ibid, 246207, behenolic acid esters, stearolio acid ester. Ibid, 264267, aryl hydroxy fatty acids. Ibid, 279199, aminometiiane disulphonic acid. Ibid., 228877, oleic acid ethyl ester, triolein. Ibid., 387850 American Patent, 1457675 diethyl diallylmalonate, diallyb barbituric acid, ethyl dialiylacetate, diethjri o-phenylenediacrylate, diplienio acid and ethyl diphenylamine-2-ca.rboxylate. 

Aryl hydroxy groups have been removed by first converting them into an ether by reaction with a heterocycle such as l-phenyl-5-chlorotetrazole (61) and then hydrogenolyzing the ether with platinum or palladium (Eqn. 20.42).97-99 other aryl ether groups that are readily hydrogenolyzed to give the benzene are the benzoxazole, 62, > sulfonates, 63, and phosphates, 64. ... 

When an aryl hydroxy or amino derivative is added to the diazonium salt solution, a union of the diazo group with the added aryl compound occurs, which is known as coupling. In this union the para hydrogen atom of the amino or hydroxy compound reacts. If the para position is already occupied then the ortho hydrogen atom reacts. If both are occupied, no coupling takes place. 

This reaction is quite useful to convert an aryl hydroxy compound to the corresponding amino derivative. 

The complexes with a M-SiRs bond are known for R = Me, but also with R = alkyl, aryl, hydroxy, chloro and fluoro. 

Similar support for the mechanism (Figure 4.13) of aryl hydroxy-lation was also obtained from studies of the tritium retention and migration which accompanies hydroxylation of 4-[ H]-anisole (57) and 3-[ H]-4-[ H]-anisole (58), and the analogous acetanilide derivatives . Isomerisation of the intermediate keto forms (59 and 60) to 4-hydroxyanisole led to the expected significant primary isotope effect (Kh > > Kj) and more tritium was observed to... 

Replacement of KCN with the highly covalent Zn(CN>2 has emerged as an additional powerful alternative because the concentration of cyanide ions, which are believed to be detrimental to the catalytic cycle, is significantly lowered. In the presence of Pd(PPh3>4, high yields of nitriles are obtained from aryl bromides at 80 °C in a few hours and from iodoanilines in 30 min.. Under Pd2(dba)3 catalysis in the presence of P(rcrt-Bu)3 or P(o-tolyl)3, even aryl bromides possessing a variety of substituents including unprotected aryl hydroxy and aryl amine functions react at mild temperatures (DMF or NMP, 80°C). Examples 12, 13, and 14 show the application of Zn( " CN)2 in carbon-14 syntheses. 

In peptide syntheses, where partial racemization of the chiral a-carbon centers is a serious problem, the application of 1-hydroxy-1 H-benzotriazole ( HBT") and DCC has been very successful in increasing yields and decreasing racemization (W. Kdnig, 1970 G.C. Windridge, 1971 H.R. Bosshard, 1973), l-(Acyloxy)-lif-benzotriazoles or l-acyl-17f-benzo-triazole 3-oxides are formed as reactive intermediates. If carboxylic or phosphoric esters are to be formed from the acids and alcohols using DCC, 4-(pyrrolidin-l -yl)pyridine ( PPY A. Hassner, 1978 K.M. Patel, 1979) and HBT are efficient catalysts even with tert-alkyl, choles-teryl, aryl, and other unreactive alcohols as well as with highly bulky or labile acids. 

Aryl, heteroaryl, and alkenyl cyanides are prepared by the reaction of halides[656-658] or triflates[659,660] with KCN or LiCN in DMF, HMPA, and THF. Addition of crown ethers[661] and alumina[662] promotes efficient aryl and alkenyl cyanation. lodobenzene is converted into benzonitrile (794) by the reaction of trimethylsiiyl cyanide in EtiN as a solvent. No reaction takes place with aryl bromides and chlorides[663]. The reaction was employed in an estradiol synthesis. The 3-hydroxy group in 796 was derived from the iodide 795 by converting it into a cyano group[664]. 

Goto et al. (386) have qualitatively studied the relationship between the structure and the ease of formation of some 2-aryl- and 2-heteroaryl-A-2-thiazolin-4-one derivatives. It is found that 2-pyridyI, 2-benzimidazoyl, and 2- 6 hydroxy-5 -methyl)-benzothiazolyl derivatives are too unstable to be isolated. 6 -Hydroxy-, 6 -methyl-, and unsubstituted 2-benzothiazoiyl derivatives, as well as naphtothiazolyl derivatives are unstable but isolable. On the other hand, 6 -methoxy-. 6 -acetoxy-. and 5, 7 -dimethyl-6 -hvdroxybenzothiazolyl derivatives as well as most of their 5-methyl substituted derivatives are stable and easily prepared. 

Similarly, 5-thiazole alkanoic acids and their salts are obtained from thioamides and /3-halo -y-keto acids (695). Thus thioarylamides condensed with 3-aroyl-3-bromopropionic acid (88) in isopropanolic solution in the presence of Na COs give first 4-hydroxy-2-aryl-A-2-thiazoline-5-acetic acid intermediates (89), which were dehydrated in toluene with catalytic amounts of p-toluene sulfonic acid to 2,4-diaryl-5-thiazole acetic acid (90) (Scheme 39) (657), with R = H or Me Ar = Ph, o-, m- or p-tolyl, o-, m-, or P-CIC6H4, 0-, m-, or p-MeOC(iH4, P-CF3C6H4, a-thienyl, a-naphthyl (657). 

Aryl 1715-1695 o-Hydroxy or amino groups shift this value to... 

Ketones C=0 continued) o-Amino-aryl or o-hydroxy-aryl ketones 1655-1635 Low because of intramolecular H bonding. 

Alkali Metal Hydroxides. Addition of base to aqueous chloroformates cataly2es hydrolysis to yield the parent hydroxy compound (11). However, the use of a stoichiometric amount of alkaU metal hydroxides can lead to the symmetrical carbonate, especially from aryl chloroformates (12,13). 

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