Use as precursor for preparation

Alkylation and arylation of the aminofuroxans are unknown as yet, presumably because of their instability under harsh conditions. However, aziridino furoxans may be used as precursors for preparation of functionalized alkylamino derivatives (Scheme 113) (88AP77). 

As mentioned in Section III, phosphomolybdate heteropoly compounds have recently been used as precursors for preparing hydrotreating catalysts. 

Cobalt porphyrins and phthalocyanines were used as precursors for preparation of carbon supported cobalt catalysts that displayed high activity in reduction of oxygen in fuel cells [9-12], These samples were prepared by deposition of cobalt phtalocyanine on active carbon following by heat treatment at 650-700°C in an inert atmosphere providing formation of Co-N structure deposited on active carbon. 

The functional groups of polyions can coordinate metal ions, thereby acting as ligands. The sorption of metal ions from solutions is a common way of embedding metal ions into multilayer polyelectrolyte films. For example, Ag" " ions were incorporated into PAA/PAH multilayers from solutions of silver acetate [104]. A variation in the pH made it possible to change the content of metal ions in the films [105]. Also, palladium ions [104] were successfully included into PAA/PAH multilayers from aqueous solutions containing [Pd(NH3)4] ions. It should be mentioned that polyelectrolyte multilayers containing metal ions can be further used as precursors for preparation of polymer-metal nanohybrids [82, 83,103-105]. 

Recently, a case study which addressed the high-temperature behavior of SiZ-rCNO ceramics indicated that they can also be used as precursors for preparing ultra-high temperature stable ceramic nanocomposites, i.e. p-SiC/ZrC (upon HT annealing of SiZrCNO in Ar atmosphere) and p-SijN /ZrN (upon HT annealing in nitrogen) (Linck, 2013). 

The preparation of ceramic powders by CVD is a promising and growing field. These powders are used as precursors for the processing of advanced ceramics, or directly as powder for such applications as abrasives. 

Several patents dealing with the use of volatile metal amidinate complexes in MOCVD or ALD processes have appeared in the literature.The use of volatile amidinato complexes of Al, Ga, and In in the chemical vapor deposition of the respective nitrides has been reported. For example, [PhC(NPh)2]2GaMe was prepared in 68% yield from GaMes and N,N -diphenylbenzamidine in toluene. Various samples of this and related complexes could be heated to 600 °C in N2 to give GaN. A series of homoleptic metal amidinates of the general type [MIRCfNROilnl (R = Me, Bu R = Pr, BuO has been prepared for the transition metals Ti, V, Mn, Fe, Co, Ni, Cu, Ag, and La. The types of products are summarized in Scheme 226. The new compounds were found to have properties well-suited for use as precursors for atomic layer deposition (ALD) of thin films. 

Acyloxy-l-cyanoalkanes [45, 46], which can be used as precursors for ketones [47], a-hydroxy ketones [48] and 1,4-dicarbonyl compounds [47], are prepared in one pot from the appropriate aldehyde, sodium or potassium cyanide, and the acylating agent under phase-transfer catalytic conditions [47-49]. Attempts to synthesize chiral cyanhydrins using chiral phase-transfer catalysts have been unsuccessful (see Section 12.3). 

Fe(CO)s], [Fe2(CO)g], [Co2(CO)8] and [Os3(CO)i2]) have been reacted with dicyanobenzene to form intrazeolite [M(Pc)] complexes [140]. Another class of materials prepared by the intrazeolite template synthesis method has been mixed ligand metal carbonyls and metal carbonyl clusters, frequently by reductive car-bonylation of metal ions in zeolite cages [175]. However, because these are frequently decomposed in situ to form, for example, nanoparticles, they are outside the scope of this chapter, and will be considered here only when they are used as precursors for metal complexes. 

High nuclearity carbonyls Rh4(CO)i2 and Rhs(CO)i6 have been extensively used as precursors for the preparation of supported rhodium catalysts. Early studies reported the use of a great variety of supports that includes metal oxides [159-166], zeolites [101, 167], polymers [168] and modified-silica surface [169]. 

The cadmium(II) complexes of thiourea and N-alkylthioureas (with alkyl groups methyl or ethyl) have been used as precursors for the preparation of TOPO-capped CdS nanoparticles (Fig. 14). The precursors are air-stable, easy to prepare and inexpensive. These compoimds decompose cleanly to give good-quality crystalline materials [122]. 

In addition to their use as precursors for alkynylboron, tin or zinc compounds, alkynylmagnesium reagents show a moderate reactivity toward the coupling with haloarenes and haloalkenes. They are often commercially available, or easy to prepare. Their main drawback is their low chemoselectivity and high nucleophilicity, which implies incompatibilities with functional groups such as nitro and carbonyl. 

In order to study the influence of a given chiral group at different positions in the precursor styrylbenzo[c]phenanthrene several carboxy styrylbenzo[c]phenanthrenes were synthesized and esterified with chiral alcohols, and the products were used to prepare hexahelicenes 76 substituted at various positions. The bromo-esters (29) were used as precursors for [6]-helicenes, substituted at position 1. 

Several carboxylic acid derivatives that might be accessible using biocatalysis were used as precursors for the synthesis of pregabaiin and could potentially be prepared using biocatalysis (Scheme 8.4). Among these, 2-carboxyethyl-3-cyano-5-methylhexanoic acid (13) and 3-cyano-5-methylhexanoic acid (5) appeared as the... 

For the preparation of monoacetals of o-phthaldehyde and reduction to precursors of isobenzofurans, see also Smith and Krtiger (85JOC5759). Dimethoxyacetals of type 33 are also used as precursors for the preparation of isobenzofurans (83CJC1987). 

Amino-1 //-1,2,4-triazole and its derivatives are frequently used as precursors for this ring via their reaction with suitable carbonyl compounds. The 5-amino-l,2,4-triazoles (27), prepared from calcium cyanide by hydrolysis to cyanamide followed by condensation with hydrazine (92MI4), reacted with the appropriate acetophenone in presence of ZnCl2 to give the... 

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