Statistical synthesis

V. G. Repin, G. P. Tartakovsky, Statistical Synthesis under the Prior Uncertainty (In Russian), Sov. Radio, Moscow, 1977... 

A spectacular application of the acyloin ester condensation was the preparation of catenaries like 11. These were prepared by a statistical synthesis which means that an acyloin reaction of the diester 10 has been carried out in the presence of an excess of a large ring compound such as 9, with the hope that some diester molecules would be threaded through a ring, and would then undergo ring closure to give the catena compound ... 

Schemes of this type were carried out by Harrison, I.T. Harrison, S. J. Am. Chem. Soc., 1967, 89, 5723 Ogino, H. J. Am. Chem. Soc., 1981, 103, 1303. For a different kind of statistical synthesis of a rotaxane, see Harrison, I.T. J. Chem. Soc., Perkin Trans. 1,1974, 301 Schill, G. Beckmann, W. Schweikert, N. Fritz, H. Chem. Ber, 1986,119,2647. See also Agam, G. Graiver, D. Zilkha, A. J. Am. Chem. Soc., 1976, 98, 5206.

The acyloin condensation was used in an ingenious manner to prepare the first reported catenane (see p. 91).727 The catenane (39) was prepared by a statistical synthesis (p. 91) in the following manner An acyloin condensation was performed on the diethyl ester of the C34 dicarboxylic acid (tetratriacontandioic acid) to give the cyclic acyloin 37. This was reduced by a Clemmensen reduction with DCI in D20 instead of HC1 in H20, thus producing a C34 cycloalkane containing deuterium (38) 728... 

Hudson, J.B. Thermodynamics of Materials A Classical and Statistical Synthesis, John Wiley Sons, Inc., Hoboken, NJ, 2004. 

The chemical constitution of rotaxanes will depend, of course, on the methods used for their elaboration. Whereas the statistical synthesis (vide infra)... 

The different strategies and methods can be combined according to their particular features. Thus the statistical synthesis relies on the threading or slipping principle, while the directed method relies only on the clipping method. 

Fig. 8 The two applied approaches to catenane synthesis prior to 1983. (a) The first statistical synthesis [58] relied upon the macrocyclization of a linear compound (7) in the presence of a deuterated cycloalkane (III) to achieve small amounts of the catenane V. (b) The first example [59] of directed synthesis by covalent templation was a catenane that formed after cleaving the covalent bonds around the aromatic core in compound 16. Reproduced with permission from [58] (copyright 1960 American Chemical Society), [59] (copyright 1964 Wiley-VCH)...

Statistical synthesis. As far back as in 1952 an idea was ventured concerning an accidental formation of a catenane during the polymerization reaction, e.g. in polyphospho-... 

These data indicated that the acyloin, cycle is intertwined with C34He3D. Initially Wasserman recovered 5.66 mg of catenane oil, the total yield being 0.0001 per cent. Subsequently Wasserman and coworkers developed other methods of statistical synthesis of catenanes. 

Chapter 13 looks at sonic particles as the fundamental unit of sound production, examining wavetables, physical particle-controlled sinusoidal synthesis, and noise/filter-based statistical synthesis of noisy sounds. 

While many possible approaches to statistical synthesis are possible, most work has focused on using hidden Markov models (HMMs). This along with the unit selection techniques of the next chapter are termed third generation techniques. This chapter gives a full introduction to these and explains how they can be used in synthesis. In addition we also show how these can be used to automatically label speech databases, which finds use in many areas of speech technology, including unit selection synthesis. Finally, we introduce some other statistical synthesis techniques. 

The statistical synthesis process and the many parameters determining a polymer product tend to make it a complex and often rather ill-defined material. However, new methods in polymer synthesis have recently evolved and existing methods have been further developed that allow much higher control of a polymer s constitution, connectivity, molar mass, configuration, and even its tertiary structure formation and self-assembly. So, the ultimate goal to prepare synthetic macromolecules with the same precision found in nature but with precisely adjusted combinations of functionality—even beyond nature—may come within reach. 

Scheme 6.1 Statistical synthesis of cholesteric and nematic GLCs. DEADC diethyl azodicar-boxylate, PPhs triphenylphosphine...

The key intermediate in Reaction Scheme 6.2, viz. 2,4-dioxo-3-oxa-bicy-clo[3.3.1]nonane-7-carboxylic acid chloride, was synthesized for esterification with nematic and chiral precursor alcohols in two consecutive steps [34] to produce a nematic GLC, (21), and a chiral molecular glass, (22). Whereas the work-up procedures were substantially simplified compared to the statistical approach, the synthesis of the key intermediate and its stability remained challenging. The 14 % overall yield of an enantiomeric chiral molecular glass turned out to be inferior to that from statistical synthesis. 

Monohydrolysis of trimethyl esters is the key to two alternative deterministic approaches as described in Reaction Scheme 6.3 [35]. About 50 % overall yield of cholesteric GLCs, (23) and (24), using pig liver enzyme as the first step in Approach (a), and a 23 % overall yield of (25) involved base catalysis in Approach (b), the former being superior to statistical synthesis with much less laborious work-up procedures. 

In view of the unique roles of cholesteric GLCs in material synthesis and device application, the commonly practiced statistical synthesis and the continuing effort in deterministic synthesis are highlighted. All factors considered, a hybrid chiral-nematic precursor is much preferred over separate chiral and nematic precursors in terms of synthesis and subsequent product separation and purification. 

The statistical synthesis shown in Table 2 for the most perceived relevant risks in the area of residence of respondents reveal that the most important factors in the influencing risk perception are educational capital, the area type (rural, mixed, urban) and house type. The access to information and the educational networks activated do allow for a better assessment of the risks involved in the area of residence. Both the area type and the house type, indicators of housing... 

The statistical method of syntl s of topological compounds can be divided into a truly statistical synthesis and a thesis with elements of directionality. Prq>aring catenanes by the statistical method is described in ddail by Sdiill in his monograph The statistical technique of synthesis of rotaxanes will be presented here in greater detail. The scheme of the technique is as follows bulky end groups are connected to a linear molecule in the presence of a macrocycle. Sudi a re kn, where the macrocycle remains imchanged, results in the formation of some amount of rotaxane and a molecular dumb-beU ... 

An interesting possibility for the formation of linear polycatenanes is the statistical synthesis technique proposed by Greek researdiers Tte tedmique consists... 

The problems of synthesis and investigaticm of polyrotaxanes are presented in the literature by a number of studies. These are researches in the field of statistical synthesis directed synthesis and synthesis with elements of directional-... 

The specific features of complexing betweai crown polyesters and metal cations indicate the impossibility of using such ccnnpkxes for a directed synthesis of poly-rotaxanes. Only their statistical synthesis with the use of free macrocyclic polycthers is feasible... 

Hudson, J. B. 1996. Thermodynamics of Materials Classical and Statistical Synthesis. New York Wiley-Interscience. 

Scheme 19. Statistical synthesis of unsymmetrically substituted derivatives of triphenylene [41]. Reagents (a) RBr/K2C03/ PhCOMe/l 16X/17 h, 26% monoacetate.

One way to obtain such dienophilic and enophilic phthalocyanines is by statistical synthesis starting from two correspondingly substituted phthalonitriles (Fig. 15.18). The Dzh isomer can be separated by column chromatography from the other five isomers [218 M. Hanack and P. Stihler, unpublished]. 

When designing synthesis instruments, we should give preference to those techniques that best fit the way we understand the sound phenomena we want to work with. For example, whilst those composers interested in timbral manipulation will be better off working with analysis and resynthesis techniques (Chapter 3), those working with scientific metaphors (e.g. dynamic systems, cellular automata, etc.) would certainly prefer to use granular or statistical synthesis methods (Chapter 5). 

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