Hydroxy-, derivatives metallated

Ana.lytica.1 Rea.gents, The chelating property of quinolines, eg, 8-hydroxy derivatives, make them useful in metal gravimetric appHcations however, few are any longer of practical importance. Amino- and sulfur-substituted quinolines have also been employed in metal analyses (105,106). 

Although isoxazoles are comparatively weak electron donors, complexes with numerous metal ions, notable metal(II) ions, have been reported. The ligands include isoxazole and its methyl, phenyl, amino and hydroxy derivatives. They are listed with references in Table 5. 

A good example is the reduction of 11-keto steroids (69) which gives only the llJ -hydroxy derivatives (70) with metal deuterides. Generally, the 1 la-alcohols are obtained in good yield by reduction with lithium in liquid ammonia-methanol mixtures. By analogy, llj -dj-lla-alcohols (71) are expected when a deuterioammonia-methanol-OD system is used. (For an alternate preparation of an 11/5-dj-l la-hydroxy steroid, see section III-C). 

There are now a number of X-ray structures for simple triazolopyridines, ylides, and metal complexes which show the molecular dimensions. The 3-pyridyl derivative 135 (94JCS(D)2651), the ester 136 (83AX(C)391), and the 3-hydroxy derivative 137 (99JMS(476)289) provide dimensions for systems 1, 2, and 4, and are shown in Fig. 2. 

Aluminum phthalocyanine (PcAlX) can be prepared from the phthalonitrile and aluminum trichloride either in refluxing quinoline138 13g or without a solvent under addition of ammonium molybdate(VI).137 The chloro compound can be transformed to a hydroxy derivative by treatment with sulfuric acid.58-140 Also, the insertion of aluminum in a metal-free phthalocyanine is possible, for example trialkylaluminum can be used.141,142... 

Formal hydration of the double bond appeared by the hydroboration-oxidation sequence. Desymmetrization reactions with catalytic asymmetric hydroboration are not restricted to norbornene or nonfunctionalized substrates and can be successfully applied to meso bicyclic hydrazines. In the case of 157, hydroxy derivative 158 is formed with only moderate enantioselectivity both using Rh or Ir precatalysts. Interestingly, a reversal of enantioselectivity is observed for the catalytic desymmetrization reaction by exchanging these two transition metals. Rh-catalyzed hydroboration involves a metal-H insertion, and a boryl migration is involved when using an Ir precatalyst (Equation 17) <2002JA12098, 2002JOC3522>. 

Two different mechanisms have been proposed for the ROP of (di)lactones depending on the nature of the organometalhc derivatives. Metal halides, oxides, and carboxylates would act as Lewis acid catalysts in an ROP actually initiated with a hydroxyl-containing compound, such as water, alcohol, or co-hydroxy acid the later would result more hkely from the in-situ hydrolysis of the (di)lac-tone [11]. Polymerization is assumed to proceed through an insertion mechanism, the details of which depends on the metal compound (Scheme la). The most frequently encountered Lewis acid catalyst is undoubtedly the stannous 2-ethylhexanoate, currently referred to as stannous octoate (Sn(Oct)2). On the other hand, when metal alkoxides containing free p-, d-, or f- orbitals of a favo-... 

The same transformation was reported to follow treatment of 17 with excess sodium hydroxide (Sequiv), in aqueous acetone. In this case, the product yield was lower. With a reduced amount of alkali, 0.5 equiv KOH, both the hydroxy derivative 140 and the difurazanyl ether-linked bis(triazolooxadiazole) 37 resulted (Scheme 21) <1999RJ01525>. As a precaution it should be noted that the strongly acidic nature of hydroxyfurazans means they readily form stable salts with amines and alkali or alkaline earth metals, and such salts show a tendency to decompose with explosion on shock, friction, or fast heating, and so should be handled with care <1999RJ01525>. 

Metallic salts of hydroxy-derivatives may be named in the customary manner. Example ... 

An important place among chelating ligands belongs to N,0-donors (Sec. 2.2.5.3) which, similarly to discussed above with N,N-donor ligand systems, allow us to create programmed metal-cycles of different size (Sec. 2.2.5.3 414, 418, 422, 424, 427, 428, 432, 433, 436, 438, 445, 446-449). To obtain metal chelates with four-member chelate unit, the interaction of, for example, 2-hydroxy derivatives of azines and metal salts is used (3.45) [52] ... 

Reactions of 1,2,4-thiadiazoles with radicals and electron deficient species are virtually unknown. Catalytic and dissolving metal reductions usually result in S—N bond cleavage. For example, the 5-anilino-3-hydroxy derivative (51) gives a good yield of l-phenyl-2-thiobiuret (52) on Zn-HCl reduction (Scheme 27). Reduction of the diamino derivative (53) gives amidinothiourea (54) from which it may be prepared by oxidation (Scheme 28). Under similar conditions, cleavage of the 3,5-diphenyl derivative (55) results in loss of sulfur and formation of benzylbenzamidine (56 Scheme 29). Reduction of 5-alkylamino-or 5-arylamino-3-alkylthio derivatives (57) with H2S in pyridine-triethylamine or sodium in liquid ammonia yields 1-substituted dithiobiurets (58 Scheme 30). 

After hydroxylation of a steroidal substrate has taken place, fission of caibon-carbon bonds may occur. Thus 9a-hydroxylation is the first stage in the fission of the B-ring. This process can be suppressed by restriction of metals (such as iron). This has been accomplished using 2,2-bipyiidyl, either alone or in combination with an absorbent such as Amberlite XAD-7. Very substantial enhancements in yield aro possible. For example 3-ketobisnorcholenol (68) gave <10% yield of the 7a-hydroxy derivative with Botryodiploida theobromae in the absence of these materials, but up to 45% vriien diey were added together (equation 23). ... 

F. Minisci, F. Recupero, G. F. Pedulli, M. Lucarini, Transition metal salts catalysis in the aerobic oxidation of organic compounds Thermochemical and kinetic aspects and new synthetic development in the presence of N-hydroxy-derivative catalysts, /. Mol. Catal. A. 63 (2003) 204-205. 

Most carbamates used as insecticides are esters of aromatic and heterocyclic hydroxy derivatives of N-methyl- and N,N-dimethylcarbamic acids. They are usually prepared by the reaction of methyl- or dimethylcarbamoyl chloride with the alkali metal salt of the corresponding hydroxy derivative, or alternatively, the hydroxy derivative is carbamoylated with methyl isocyanate (Gysin, 1952). 

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