The Andersen method

The highly stereoselective synthesis of optically active sulfoxides using the methodology first developed by Andersen in 1962 is still the most important and widespread approach used today [9,10]. The method is based on the reaction of 

Dialkyl arenesulfinylmethanephosphonates are available by S-oxidation of the corresponding dialkyl arenesulfenylmethanephosphonates or by reaction of anions derived from dialkyl methanephosphonates with sulfinate esters. With regard to the synthesis of optically active a,P-unsaturated sulfoxides, the former method may not be applied in the absence of a reliable, highly enantioselective 5-oxidation procedure without recourse to resolution methods, while the latter method suffers from the relatively polar nature of dialkyl arenesulfinylmethanephosphonates, which renders their chromatographic separation tedious and costly. 

The first examples of the use of the Knoevanagel-type condensation for the synthesis of a,p-unsaturated sulfoxides were made by Ogura and Tsuchihashi, who prepared racemic ketene thioacetal monoxides by the condensation of methyl 

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In the foregoing treatments of pressure feedback, the simulation volume retains its cubic form, so changes consist of uniform contractions and expansions. The method is readily extended to the case of a simulation region in which the lengths and directions of the edges are allowed to vary independently. Parrinello and Rahman [31] and Nose and Klein [32] extended the Andersen method to the case of noncubic simulation cells and derived a new Lagrangian for the extended system. Though their equations of motion are... 

Both enantiomers of methyl p-tolyl sulfoxide are available from the above procedure by selection of the appropriate diethyl tartrate. This procedure describes the preparation of (S)-(-)-methyl p-tolyl sulfoxide which is not easy to prepare by the Andersen method " using (+)-raenthol. 

This chapter does not consider the Andersen method this is discussed by Allin in Chapter 2. Attention is focused on the asymmetric oxidation of sulfides to sulfoxides ( sulfoxidation ). Cases in which the chiral auxiliary is connected to the sulfide are detailed first, then stoichiometric and, finally, catalytic oxidations are discussed. 

There are several ways to produce chiral sulfoxides. The resolution of a racemic mixture is seldom used. The main approach is the Andersen method which is based on the stereoselective transformation of a sulfmate deriving from a cheap alcohol, usually (-)-menthol (Figure 5). 

The LMTO method [58, 79] can be considered to be the linear version of the KKR teclmique. According to official LMTO historians, the method has now reached its third generation [79] the first starting with Andersen in 1975 [58], the second connnonly known as TB-LMTO. In the LMTO approach, the wavefimction is expanded in a basis of so-called muffin-tin orbitals. These orbitals are adapted to the potential by constmcting them from solutions of the radial Scln-ddinger equation so as to fomi a minimal basis set. Interstitial properties are represented by Hankel fiinctions, which means that, in contrast to the LAPW teclmique, the orbitals are localized in real space. The small basis set makes the method fast computationally, yet at the same time it restricts the accuracy. The localization of the basis fiinctions diminishes the quality of the description of the wavefimction in die interstitial region. 

Busscher N, Kahl J, Huber M, Andersen J O, Mergardt G, Doesburg P, Paulsen M, Kretschmer S, de Weerd A and Meier-Ploeger A (2004), Validation and Standardization of the Biocrystallization Method Development of a Complementary Test to Assess Qualitative Features of Agricultural and Food Products, Triangle report Nr. 1, University Kassel, Louis Bolk Instituut and Biodynamic Research Association Denmark. 

These examples illustrate the procedure used in the Andersen-Beyer-Watson-Yoneda method. The hrst example shows moderate agreement the second shows poor agreement. Generally, it is preferable to consider the group substitutions in the same order as has been used in the presentation of the tables. The best agreement with experimental values, when they are known, has been obtained by using the minimum number of substitutions necessary to construct the molecule. For cases in which several alternative routes with the minimum number of substitutions are possible, the average of the different results should be used. 

Andersen et a/.," with a saccharine-particle method, found a weak positive association between tracheobronchial clearance and nasal clearance. A strong positive correlation would have indicated that information about the tracheobronchial clearance rate can be derived by studying clearance rates in the nose, which is more accessible. The saccharine method was shown to be a useful clinical tool for evaluating the status of the nasal mucociliary function in human subjects exposed to ambient pollutants or to controlled concentrations of specific pollutant gases or aerosols. 

Another method of controlling the temperature that can be used in CP MD is the stochastic thermostat of Andersen.27 In this approach the velocity of randomly selected nucleus is rescaled this corresponds in a way to the stochastic collisions with other particles in the system. Therefore, this approach is often called a stochastic collision method. The Andersen thermostat has recently been shown28 to perform very well in the Car-Parinello molecular dynamic simulations of bimolecular chemical reactions. 

Nucleophilic substitution on chiral sulfur derivatives (the so-called Andersen method)... 

The purpose of this article is to present recent developments in the preparation of optically pure sulfoxides using both methods, mainly from 1990 to the present. Emphasis has been given to the bibliographic impact of each method. An application section is included after each route, especially in the case of variation in the Andersen methodology, where important advances have been achieved. It is not the aim of this article to review the chemistry of chiral sulfoxides—several excellent review articles have appeared on this subject, from the seminal review by Solladie19 in 1981 to other recent reviews.20 The literature has been surveyed up to January 1999. The preparation and utilization of chiral sulfoxides in asymmetric synthesis have been the subject of valuable comprehensive as well as specialized accounts which should be consulted for details and considered as complementary to this article. 

A method that makes available aromatic and aliphatic aldehyde derived sulfin-imines 47, for the first time, was recently introduced by Davis and co-workers.23,36 This one-pot procedure entails treatment of the Andersen reagent 40 with LiHMDS to generate 44 which subsequently reacts with the lithium methoxide by-product to produce silyl sulfinamide anion 46. Reaction of 46 with the aldehyde in a Peterson-type olefination reaction affords the sulfinimine 47 in >96% ee. This method was highly effective for the preparation of arylidene sulfmamides 47 (R = aryl) which were usually obtained in 60-76% yield although the alkyl counterparts... 

As for the MD method in this ensemble, we just present the Nose-Andersen algorithm [119-121]. The equations of motion in (4.11)-(4.14) are now generalized as follows ... 

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