General Preparation Methods

Samples with 55 to 60.5 at.% Se were prepared from the pulverized elements in a U-shaped quartz tube at 10 Torr with separation of La and Se to avoid quick reaction. The temperature was increased gradually up to 320°C within 45 to 50 h, from 350 to 500°C within 78 to 80 h, and from 500 to 900°C within 15 to 20 h where the samples were held for another 48 to 50 h. The homogenized samples were then pressed under 250 kg/cm and sintered at 940 to 950°C for 48 to 50 h, Kagramanova et al. [1]. Homogeneous samples with 50 to 70 at.% Se were obtained when the products of ampule syntheses were diffusion annealed at 1100°C for 50 to 60 h. Reaction with the quartz wall was eliminated by use of a corundum coated container, Yarembash et al. [2]. 

---

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. ... 

---