Procedures for Preparing Derivatives

One of the principal tests for the correct identification of an unknown compound is to convert the compound by a chemical reaction to another known compound. This second compound is called a derivative. The best derivatives are solid compounds, because the melting point of a solid provides an accurate and reliable identification of most compounds. Solids are also easily purified through crystallization. The derivative provides a way of distinguishing two otherwise very similar compounds. Usually, they will have derivatives (both prepared by the same reaction) that have different melting points. Tables of unknowns and derivatives are listed in Appendix 1. Procedures for preparing derivatives are given in Appendix 2. 

Procedures for preparing derivatives from amines can be found in Appendix 2. 

Note "d" indicates "decomposition" "s" indicates "sublimation." See Appendix 2, "Procedures for Preparing Derivatives."... 

In agreement with the results of Cattelain, further methylation of the 3-methylmercapto derivative (96) results practically exclusively in 2-methyl-3-methylmercapto-5-oxo-2,5-dihydro-l,2,4-triazine (97). Further methylation of 5-methylmercapto derivative (90) yields 2-methyl-5-methylmercapto-3-oxo-2,3-dihydro-l,2,4-triazine (100). Their structure was confirmed by acid hydrolysis leading to 2-methyl-3,5-dioxo derivatives (62), As was already mentioned, this reaction is a suitable general procedure for preparing the 1-alkyl derivatives of 6-azauracil. ... 

Selenoaldehydes 104, like thioaldehydes, have also been generated in situ from acetals and then directly trapped with dienes, thus offering a useful one-pot procedure for preparing cyclic seleno-compounds [103,104], The construction of a carbon-selenium double bond was achieved by reacting acetal derivatives with dimethylaluminum selenide (Equation 2.30). Cycloadditions of seleno aldehydes occur even at 0 °C. In these reactions, however, the carbon-selenium bond formed by the nucleophilic attack of the electronegative selenium atom in 105 to the aluminum-coordinated acetal carbon, may require a high reaction temperature [103], The cycloaddition with cyclopentadiene preferentially gave the kinetically favorable endo isomer. 

Another procedure for preparing 4-hydroxy-4,5-dihydroisoxazole 2-oxides derivatives in 86-100% yield, and published by the same group [27], is based on an oxidative cleavage of D-mannitol-derivatives furnishing 2 equiv. of identical enantiopure (2R)-2-methanesulfonyloxyaldehydes which can react with a-nitroacetate in the usual manner. 

An improved procedure for preparing urea derivatives involves reaction of isocyanates or isothiocyanates with 4(5)-aminoimidazole (25 R = H) in tetrahydrofuran solution [92JCS(P1)2779]. A THF solution of 4(5)-aminoimidazole (25 R=H) generated in situ and then treated with the appropriate reagent gave either lV-imidazole-4-yl-AT-phenylurea (56 X = 0) (32%) or AT-imidazoM-yl-A/ -phenylthiourea (56 X = S) (21%). 

Among the oxidative procedures for preparing azo compounds are oxidation of aromatic amines with activated manganese dioxide oxidation of fluorinated aromatic amines with sodium hypochlorite oxidation of aromatic amines with peracids in the presence of cupric ions oxidation of hindered aliphatic amines with iodine pentafluoride oxidation of both aromatic and aliphatic hydrazine derivatives with a variety of reagents such as hydrogen peroxide, halogens or hypochlorites, mercuric oxide, A-bromosuccinimide, nitric acid, and oxides of nitrogen. 

Advantages of this Procedure for Preparing Multispecific Derivatives... 

Kita and co-workers have developed a concise and high-yielding procedure for preparing the pyrroloiminoquinone derivatives (158), which are key precursors of antitumor marine alkaloids, makaluvamine D (54), I (55), and M (56), from the phenol ether derivatives (157) bearing an alkylazido side chain using PIFA-TMSOTf [122] (Scheme 30). 

D. Lafont, P. Boullanger, O. Cadas, and G. Descotes, A mild procedure for preparation of 1,6-anhydro-jS-D-hexopyranoses and derivatives, Synthesis, (1989) 191-194. 

Based on published procedures for preparing both di- and tri-N-protected tert-butoxycarbonyl (Boc) cyclam derivatives [27], we developed the alternate procedure shown in Scheme 2 for obtaining the tri-branched species 11 [28] as well as related procedures for the new tri-branched derivative 12 (see Scheme 3) [28], the linearly linked derivative 13 [28] and the linked cyclic derivative 14 [29], In the case of the phloroglucinol derivative, tri-Boc protected cyclam was first acylated with chloroacetyl chloride the resulting chloromethylamide was then used to trialkylate phloroglucinol in DMF at 70 °C over caesium carbonate as outlined in Scheme 3. Subsequent... 

The procedures for preparing sodium amide and the sodium derivative of benzyl cyanide are described in Organic Syntheses.a Another procedure for preparing sodium amide 4 is convenient and should be equally satisfactory. 

This section will provide brief accounts of some representative synthetic procedures for preparation of solutes in superacidic media and of compounds which are derived from superacids and which owe their peculiar properties to their formation and stability under extremely weakly or strongly basic conditions. A large proportion of the examples will, of necessity, be drawn from studies using HF as solvent or reactant. This is because, in the case of HF, somewhat more inorganic chemistry has been published, to date, on acid-base properties of the solvent itself, on the nature of solutes, on unusual solutions produced in the solvent or on compounds derived from the solvent than is the case for HS03F, with even less available for CF3S03H. 

The best general procedure for preparing 2-substituted phenox-azines is the pyrolytic condensation of o-chloronitrobenzene derivatives with sodium o-bromophenolate,20,29 followed by reduction with stannous chloride or with iron filings in acetic acid and subsequent cyclization of the ether 10. If the ether 10 is previously A-formylated,... 

This general procedure for preparing N-alkylphenoxazine derivatives was not successful in the case of methyl phenoxazine-4-car-boxylate, where sodamide reacts with the substituent.62... 

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