Coordinates active

To achieve catalytic enantioselective cycloaddition reactions of carbonyl compounds, coordination of a chiral Lewis acid to the carbonyl functionality is necessary. This coordination activates the substrate and provides the chiral environment that forces the approach of a diene to the substrate from the less sterically hindered face, introducing enantioselectivity into the reaction. 

Polar and coordinatively active functional groups are structural elements frequently found in the constitution of crystal inclusion hosts, mainly including conventional host molecules7 . Typical examples are urea (2), thiourea (5), hydroquinone (4), Dianin s compound (5), deoxycholic add (6) or simply water (Fig. 1). This was the reason to assume that functional groups play an important part in the construction of crystal inclusion compounds. 

Incorporation of coordinatively active complementary (functional) groups (in the host and the guest molecule) is an essential part of the coordinatoclathrate idea (see Sect. 2.2). In other words, in the absence of functional groups (Fig. 13), a so-called coordinatoclathrate is unimaginable. Also, under these circumstances coordinative linkage of the host molecules with each other to form a recticular matrix is not applicable (see. Sect. 2.1). 

We need to point additionally to the evolution of special organs, glands, which have stored chemical message systems to help coordinate activities and are associated with nerves and the brain (Figure 8.6 and Table 8.3). Glands are advantageous in organisation as chemical substations connected to different remote parts of the... 

An orderly system for interaction of the authorities on all levels including lifeguards, ecological, sanitary and epidemiological service, specialized from the radiological protection organizations was created in the Dnepropetrovsk district in order to counteract with a well-timed reaction to any information about suspicious for radiation objects. As a result of the coordinated activities of all interested services, now it takes less than one day from the incoming of the information on suspicious radiation object till its neutralization. 

The hydration of alkynes represents a prime example in which simple coordinative activation by transition metal complexation greatly facilitates an otherwise very slow chemical process (Equation (107)). This reaction has been a long-studied problem, but only recently have alternatives to the classical use of catalysts such as Hg(n) salts been sought. These new catalyst systems typically display much enhanced reactivity, and some can mediate an anti-Markovnikov hydration through a novel mechanism (Table 1). 

Scheme 10 Metal coordination activates enediynes by drastically reducing the distance between the acetylenic carbons.

The objects can also be detailed or abstracted. A seminar company has a Sales department and an Operations department a Seminar System, which helps coordinate activities and a portfolio of courses, each of which deals with a number of Subjects (see Figure 1.9). As before, boxes are the default representation of object types. We can use stick figures... 

Odour measurement and control is just one of the many aspects of the treatment and use of organic sludges and liquid animal wastes considered within the COST 681 coordination activity. But it is a very important aspect and one which is receiving particular... 

The Human Use Review Office was charged with administering and coordinating activities of the Army Investigational Drug Review Board, the U.S. 

Another point of such coordination activity is the specific interaction of the solvents containing heteroatoms with cation-radicals having a suspended unpaired electron (cf Chapter 3). A pertinent example in this context is the interaction between the dialkylsulfide cation-radicals and the oxygen belonging to the water molecule. Such interaction enhances stability of the coordinated cation-radical ... 

A series of heteroatom substituted carbodiphosphoranes C PR2ECH(CF3)2 2 have been prepared in the last 10 years by various groups as shown in Fig. 6. The main synthetic approach consists of the reaction of hexafluoroacetone or thioacetone with the related diphosphines R2P-CH2-PR2 [25, 26]. The bent structure with a P-C-P angle (140°) confirms the double ylidic nature [27] and a related chemistry to C(PPh3)2 is expected however, no reports about coordination activities were reported so far. Theoretically, double alkylation at the heteroatoms of the dianion in Fig. 9 would lead to the substituted carbodiphosphoranes. The amino derivative C(P NMe2 3)2 has a linear structure and was not investigated further [28]. 

Part of quality management (coordinated activities to direct and control an organization with regard to quality) focused on fulfilling quality requirements [ISO 9000]... 

Both bridged and unbridged C2v-symmetric metallocenes, mostly the unsubstituted biscyclopentadienyl initiators, but also others such as (CH3)2SiFlu2ZrCl2, have been studied. These initiators are achiral, and their two coordination (active) sites are both achiral and homotopic. The result is that atactic polymer is formed via chain end control. Modest tendencies toward slight isotactic or syndiotactic placement are observed for some initiators, depending on the temperature and other reaction conditions. 

The two coordination (active) sites of a meso Cs metallocene are diastereotopic and nonequivalent, but achirotopic. Each site resides in an achiral environment and polymerization produces a highly atactic polymer, although the regioselectivity is very high, even higher than the best C2 metallocenes. Unlike some C2v metallocenes, there are no reported cases of even modest stereoselective polymerization, either syndioselective or isoselective, due to chain end control. 

In contrast to monofunctional (thio)urea organocatalysts, bifunctional catalyst structures enable simultaneous coordination, activation, and suitable relative orientation of both reaction components (the electrophile and the nucleophile) resulting in high... 

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