Acylation Alkoxy derivatives

Moreover, there are several patents and reports on cephalosporins and 7-alkoxy derivatives thereof, which are characterized by a pyridazine-derived substituent attached to the thiazine ring. Some typical examples are given in formulae (126) [347-356], (127) [357], (128) [358], (129) [359, 360] and (130) [355, 361-363] in which R1 represents a variable acyl group. 

The resistance of the furoxan ring to chemical attack allows derivatives to be prepared via the reactions of the substituents (Section 4.22.3.4). Carboxylic acids are available by permanganate oxidation of methyl derivatives or by hydrolysis of the corresponding esters reaction with ammonia affords carboxamides. Acylfuroxans provide a source of hydroxyalkyl compounds by reduction, and oximes, for example, via nucleophilic addition. Acylation and oxidation of aminofuroxans allows the amide and nitro derivatives to be prepared. Nucleophilic displacements of nitro substituents can take place, but can be somewhat hazardous on account of the explosive nature of these compounds. Alkoxy derivatives are formed with sodium alkoxide, while reaction with thiolate anions yields sulfides, from which sulfones can be synthesized by peracid oxidation. Nitrofuroxans have also been reduced to... 

Controlled oxidation of A-acyl-piperidines and -pyrrolidines can be used to prepare 2-alkoxy derivatives or the equivalent enamides, which are useful general synthetic intermediates. The former are susceptible to nucleophilic substitution under Lewis-acid catalysis, via Mannich-type intermediates, and the latter can undergo electrophilic substitution at C-3 or addition to the double bond. 

Alkylation and arylation of 1,2,3-benzotriazin-4(3//)-one (1) gave the /V3-alkyl 3,. V2-alkyl 4. or the alkoxy derivatives 5, or mixtures thereof, depending on the conditions and reagents used.7,8 90,236,269,270 In general, acylation occurs at the nitrogen in position 3.7... 

Alkoxy-bis-[acyloxy]-methane sind aus Alkyloxy-dichlor-methanen mit Carbonsauren in Anwesenheit tert. Amine bei 0-20° (53—88%)170,171 herstellbar. Mit einer analogen Reak-tion sind entsprechende N-Acyl-aminosaure-Derivate zuganglich (52—85%)170,172. Fuhrt man die Umsetzungen in Abwesenheit tert. Amine aus, so resultieren Carbonsaure-chlori-de neben Ameisensaure-alkylestern als Hauptreaktionsprodukte170. 

Regarding the S-acyl alkoxy chalcogenides [RC(0)E0R E=S, Se, Te], a few sulfur derivatives 123 RC(0)S0R have been prepared from acylsulfenyl chlorides with alcohols in the presence of pyridine [100,102]. The aromatic derivatives 123 (R=aryl) can also be obtained in good yields using aroylsulfenyl bromides with alcohols [189,253]. 

Organo-phosphonium salts can be regarded as derived from the parent tetrahedral phosphonium cation, PH J and can be represented as (6.359), where R, R, etc. can be H, halogen, alkyl, aryl, acyl alkoxy, amino, etc., and X can be halogen or other anionic group. When four different groups are attached to the P atom, enantiomorphic forms are possible (Chapter 14.2). The term quasi-phospho-nium is sometimes used to describe species in which one or more of the atoms directly bonded to phosphorus is neither C or H. 

Polymerization of MCMs can be accompanied by interaction of the monomer with an initiator (catalyst), which also results in the generation of anomalous units in the chains. These types of reactions have scarcely been studied. It is known, however, that alkoxy derivatives of many metals efficiently react with peroxide initiators. Thus benzoyl peroxide (BP) readily reacts with alkyl titanates to give titanimn acylates (Bu0)3Ti-0-Ti(0Bu)20C0Ph PhC00Bu) and with allyltrimethyltin to give allyl benzoate and trimethyltin benzoate in quantitative yield. Therefore, BP... 

I. B. Sivaev, E. G. Balandina, V. I. Biegadze. Synthesis and NMR spectra of the hydroxyundecahydro-c/ojo-dodecaborate piijHuOH] and its acylated derivatives. Russ. Chem. Bull,. 1996, 45, 683-686 (c) I. B. Sivaev, S. Sjoberg, V. I. Bregadze, D. Gabel. Synthesis of alkoxy derivatives of dodecahydro-c/ojt>-dodecaborate anion Pli2H,2]. Tetrahedron Lett., 1999, 40, 3451-3454. 

Alkoxy titanium acylate derivatives coordinated with a phosphite diester (phosphonate diester) can be prepared by reaction of a tetraalkyl titanate and an equal molar amount of a carboxyUc acid, such as methacrylic acid or isostearic acid, and a phosphite or phosphonate diester, such as dibutyl hydrogen phosphite (103). These materials reduce the viscosity of a composite system, improve... 

When large groups, such as phenyl, bromo, ethoxycarbonyl or nitro are attached at position 3, the principal products are l-alkylcinnolin-4(l/f)-ones. Cyanoethylation and acetylation of cinnolin-4(l/f)-one takes place exclusively at N-1. Phthalazin-l(2/f)-ones give 2-substituted derivatives on alkylation and acylation. Alkylation of 4-hydroxyphthala2in-l(2/f)-one with an equimolar amount of primary halide in the presence of a base leads to 2-alkyl-4-hydroxyphthalazin-l(2/f)-one and further alkylation results in the formation of 4-alkoxy-2-alkylphthalazinone. Methylation of 4-hydroxy-2-methyl-phthalazinone with dimethyl sulfate in aqueous alkali gives a mixture of 4-methoxy-2-methylphthalazin-l(2/f)-one and 2,3-dimethylphthalazine-l,4(2//,3//)-dione, whereas methylation of 4-methoxyphthalazin-l(2/f)-one under similar conditions affords only 4-methoxy-2-methylphthalazinone. 

Treatment of a-alkoxy-substituted iron acyl complexes 20 with bromine in the presence of an alcohol produces free acetals 22 with loss of stereochemistry at the center derived from the a-carbon of the starting complexl2,49. Electron donation from the alkoxy group allows formation of the oxonium intermediate 21, which is captured by the alcohol to generate the product acetal. 

The acylation of the carbanions derived from nitroalkanes with acyl imidazoles or alkoxy-carbonylimidazoles takes place at the carbon atom to yield a-nitro ketones or a-nitro esters, respectively (Eq. 5.10).21 The lithium salts of nitroalkanes were isolated and used in THF or DMSO in the original procedure. Later, potassium salts generated in situ on treatment with r-BuOK in DMSO are reactive enough to give a-nitro ketones in good yield (Eq. 5.11).22... 

The chemical diversity of carboxylic acid esters (R-CO-O-R ) originates in both moieties, i.e., the acyl group (R-CO-) and the alkoxy or aryloxy group (-OR7). Thus, the acyl group can be made up of aliphatic or aromatic carboxylic acids, carbamic acids, or carbonic acids, and the -OR7 moiety may be derived from an alcohol, an enol, or a phenol. When a thiol is involved, a thioester R-CO-S-R7 is formed. The model substrates to be discussed in Sect. 7.3 will, thus, be classified according to the chemical nature of the -OR7 (or -SR7) moiety, i.e., the alcohol, phenol, or thiol that is the first product to be released during the hydrolase-catalyzed reaction (see Chapt. 3). Diesters represent substrates of special interest and will be presented separately. 

The 3-acyl-2(3F/)-oxazolones function as good dienophiles in cycloaddition reactions with cyclic 2,4-dienes such as cyclopentadienes and anthracenes. Thus, the thermal reaction of 3-acetyl-2(37/)-oxazolone with cyclopentadiene and the hexachloro and hexamethyl derivatives gives endo-cycloadducts exclusively. In particular, the chiral cycloadducts 221 and 223 derived from the diastereoselective Diels-Alder reactions of 3-(2-exo-alkoxy-l-apocamphanecarbonyl)-2(3/7)-oxazo-lones with hexamethylcyclopentadiene and 9,10-dimethylanthracene, respectively, are highly useful as chiral 2-oxazolidinone auxiliaries. The conformationally rigid roofed structures play a crucial role in affording excellent chiral induction (Fig. 5.54). 

The two main resin linkers developed so far are shown in Scheme 18, i.e. tris(alk-oxy)benzylamide- 412 and 4-alkoxybenzylamide-type linkers)341 the former being TFA labile and thus fully compatible with Fmoc/tBu and the latter strongly acid labile and correspondingly compatible with Boc/Bzl chemistry. As shown in the case of the tris(alk-oxy)benzaldehyde handle such handles may be introduced into the C-terminal amino acid ester by reductive amination, and after suitable N -protection coupled to amino-functionalized resins (see Scheme 18). Alternatively, the tris(alkoxy)benzaldehyde-functionalized resin, BAL resin, (see Scheme 14) is used to link the C-terminal amino acid ester by reductive amination. To overcome the difficult acylation of the V -arylamino acid ester derivative on resin (best results with 10 equivalent symmetrical anhydrides), synthesis in solution of the C-terminal dipeptide building block containing the amide handle followed by its attachment to the resin has been proposed)341 ... 

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