General Preparative Methods

Fletcher and coworkers have utilized the poly-O-acylaldofuranosyl halides. Treatment of crude tri-O-benzoyl-D-ribofuranosyl bromide with sodium phenoxide in 1,2-dimethoxyethane gave phenyl /9-D-ribo-furanoside88 use of sodium methoxide gave methyl /9-D-ribofuranoside.88 

The subject of glycosylamines has already been reviewed in this Series,80 and the nomenclature of these compounds, formerly called JV-glycosides, amides, anilides, etc., was discussed. 

A new route, from 1-thio-D-aldohexofuranosides, was developed by Wolfrom and coworkers ethyl 1-thio-a-D-glucofuranoside was converted by chlorine into the chloride,101 arid this was condensed with the chloro-mercuri derivative of a 2,6-diacetamidopurine to give, on partial deacetylation, a 2-acetamido-9- f-D-glucofuranosyladenine.70 D-Galactofuranosyl analogs were also prepared. 

In 1946, Berger and Lee102 heated D-ribose with aniline in ethanol, and obtained a crystalline product to which they ascribed an a-n-furanoid structure. This iV-phenyl-a-D-ribofuranosylamine showed mutarotation in water, and was hydrolyzed by water, by aqueous acid, and by alkali. It was distinguished from the pyranoid isomer by differences in optical rotation and mutarotation. The furanoid structure was allegedly established 

Ellis and Honeyman80 have raised strong doubts as to the validity of the structural determinations that have been applied to glycosylamines these doubts are based on the fact that such compounds are readily isomerized, as evidenced by their mutarotation. The formation of a trityl ether cannot be considered valid evidence for the presence of a primary hydroxyl group in the compound tritylated, and periodate oxidation, which is often excessive, may lead to faulty conclusions. 

The successful preparation of metal-R], complexes usually requires considerable attention to experimental detail in particular, the exclusion of oxygen is usually essential. Only the most commonly used routes are discussed here and examples are chosen from a wide range of complexes in order to illustrate their common chemistry. 

Grignard reagents are not always alternatives to the alkali metal derivatives organolithium reagents are frequently the more reactive and more readily give fully alkylated or arylated products. 

Other related alkylating reagents which have been used are dimethylzinc, tetraethyl-lead, trimethylaluminium and dialkylcadmium compounds (see pp. 238-239, 254-255). 

Qj) From complex metal anions and organic halides 

Transition metal carbonyls and n -cyclopentadienyl metal carbonyls form 

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One of the most dramatic developments in the chemistry of N2 during the past 30 years was the discovery by A. D. Allen and C. V. Senoff in 1965 that dinitrogen complexes such as [Ru(NH3)5(N2)1 could readily be prepared from aqueous RUCI3 using hydrazine hydrate in aqueous solution. Since that time virtually all transition metals have been found to give dinitrogen complexes and several hundred such compounds are now characterized.Three general preparative methods are available ... 

As mentioned in last year s Report, aromatic phosphoramidates have been used to protect 5 -phosphoryl groups in the stepwise synthesis of oligodeoxyribonucleotides. The appropriate monomer units are coupled with DCC and the phosphoramidate protecting group is removed when required with isoamyl nitrite. A rapid and general preparative method for oligonucleotides has been developed based on phosphoramidates of the highly lipophilic 4-aminophenyltriphenylmethane (25). Purification of... 

General Preparation Methods of Aluminum-Deficient Zeolites... 

DePuy, as early as 1966 [14], reported that cw-1-methyl-2-phenylcyclopropanol gave exclusively deuterated 4-phenyl-2-butenone in 0.1 M NaOD/D20/dioxane. However, homoenolates derived from simple cyclopropanols by base-induced proton abstraction fail to react with electrophiles such as aldehydes and ketones, which would afford directly 1,4-D systems. Lack of a reasonably general preparative method was another factor which impeded the studies of homoenolate chemistry. For this reason, in the past twenty years more elaborated cyclopropanols, which might be suitable precursors of "homoenolates", have been prepared and studied. 

In spite of the synthesis of very interesting compounds, the latter are not general preparative methods. 

The majority of transition metal complexes [M]-CL2 are known with C(PPhs)2 as ligand CL2 while the coordination ability of other symmetrical carbodiphosphoranes remains unexplored as yet. General preparation methods to introduce this ligand consists in a reaction between the free double ylide and a transition metal complex with a labile bonded ligand or compounds with a vacant coordination site. 

Under the heading Preparation or Production, preparative processes are described briefly. Chemical equations are shown wherever applicable. While Preparation refers to laboratory method or a general preparative method, the term Production refers to commercial manufacturing processes. For many compounds both historical preparative methods and those in common use are described. 

Beryllium dialkyls BeR2 are best made by one of the most general preparative methods for organometallics, by heating elemental beryllium with the corresponding mercury alkyl HgR2 ... 

The diazotization of 5-aminotetrazole as a general preparative method for 5-substituted tetrazoles with versatile simple substituents is still important. For instance, the preparation of N-unsubstituted 5-nitrotetrazole 397 through 5-nitrotetrazole sodium salt tetrahydrate <1997RJ01771> is a significant achievement of the last decade and demonstrates new features of the amino group reactivity in 5-aminotetrazole derivatives (Scheme 46). 

Many catalysts consist of an active component or components (see Section B) deposited on a support (such as silica, alumina, carbon). The role of the support may be to improve the properties (e.g. stability) of the active componcnt(s), or to participate directly in the catalytic reaction (e.g. by providing acidic sites). The following terms define general preparation methods. 

This procedure is a general preparative method for metalla-0-diketone molecules where the metalla moiety may be either the ra-tetracarbonylrhenium or the carbonyl-7 5 -cyclopentadienyliron fragment.6 In each case the diacylmetallate monanion is prepared from an acyl complex, and then this anion is protonated at low temperature. The synthesis of the metalla-acetylacetone complex presented here utilizes acetylpentacarbonylrhenium as the acyl complex. The preparation of this acetyl complex from acetyl chloride and sodium penta-carbonylrhenium is provided, also. 

A second convenient general preparative method involves the addition of methyl-amine to methyl or ethyl acetate9,10. The mixture is allowed to stand for approximately two weeks under anhydrous conditions. This procedure yields crude NMA after removal of the alcohol by-product and the unreacted starting materials by distillation under vacuum. 

Perhalogeno alkyls are useful reagents for transferring CX3, CX2, or CX groups to other elements. A fairly general preparative method is... 

The action of hydrogen bromide or hydrogen chloride on diazo ketones represents a general preparative method (50-90%) for pure halomethyl alkyl, halomethyl aryl, or halomethyl heterocyclic ketones. N ... 

Research carried out in the author s laboratory, including general preparative methods... 

The reaction of 3a,5a-cyclo-6-hydroxy steroids with azoimide in the presence of boron fluoride represents a general preparative method for the preparation of 3j8-amino-5,6-unsaturated steroids which can be thus obtained in excellent yields. The intermediate in this reaction is 6j3-azido-3a,5a-cycloconanine which undergoes homoallylic rearrangement to yield 3 -azido-5,6-unsaturated steroid (115). By this procediu e conamine was prepared in pme condition for the first time (76). 

The use of anhydrous hydrogen fluoride for the preparation of acyl fluorides, first proposed by Colson and by Fredenhagen, was developed into a general preparative method by Olah and Kuhn. A procedure for the preparation of benzoyl fluoride has appeared in Organic Syntheses. ... 

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