Inexpensive reagents

Optically Active PO. The synthesis of optically pure PO has been accompHshed by microbial asymmetric reduction of chloroacetone [78-95-5] (90). (3)-2-Meth5loxirane [16088-62-3] (PO) can be prepared in 90% optical purity from ethyl (3)-lactate in 44% overall yield (91). This method gives good optical purity from inexpensive reagents without the need for chromatography or a fermentation step. (3)-PO is available from Aldrich Chemical Company, having a specific rotation [0 ] ° 7.2 (c = 1, CHCl ). 

The present procedure provides a convenient two-step route to 2-(hydroxy-methylJallyltrimethylsilane using relatively inexpensive reagents. Other approaches require more steps and expensive chloromethyltrimethylsilane. ... 

The in situ cyanosilylation of p-an1saldehyde is only one example of the reaction which can be applied to aldehydes and ketones in general. - The simplicity of this one-pot procedure coupled with the use of inexpensive reagents are important advantages over previous methods. The silylated cyanohydrins shown in the Table were prepared under conditions similar to those described here. Enolizable ketones and aldehydes have a tendency to produce silyl enol ethers as by-products in addition to the desired cyanohydrins. The... 

The most important olefins used for the production of petrochemicals are ethylene, propylene, the butylenes, and isoprene. These olefins are usually coproduced with ethylene by steam cracking ethane, LPG, liquid petroleum fractions, and residues. Olefins are characterized by their higher reactivities compared to paraffinic hydrocarbons. They can easily react with inexpensive reagents such as water, oxygen, hydrochloric acid, and chlorine to form valuable chemicals. Olefins can even add to themselves to produce important polymers such as polyethylene and polypropylene. Ethylene is the most important olefin for producing petrochemicals, and therefore, many sources have been sought for its production. The following discusses briefly, the properties of these olefmic intermediates. 

Ethylene reacts by addition to many inexpensive reagents such as water, chlorine, hydrogen chloride, and oxygen to produce valuable chemicals. It can be initiated by free radicals or by coordination catalysts to produce polyethylene, the largest-volume thermoplastic polymer. It can also be copolymerized with other olefins producing polymers with improved properties. Eor example, when ethylene is polymerized with propylene, a thermoplastic elastomer is obtained. Eigure 7-1 illustrates the most important chemicals based on ethylene. 

Secondary alcohols are oxidized easily and in high yield to give ketones. For large-scale oxidations, an inexpensive reagent such as Na2Cr207 aqueous acetic acid might be used. For a more sensitive or costly alcohol, however, pyridinium chlorochromate is often used because the reaction is milder and occurs at lower temperatures. 

This synthetic process is applicable to the preparation of other ketene acetal derivatives of /3-alkoxy alcohols. Examples include the ketene acetal derivatives of tetrahydrofurfuryl alcohol and l-methoxy-2-propanol.3 There are a number of advantages in its use, including a simple, time-saving procedure, readily available and inexpensive reagents, and good yields of ketene acetal obtained by a one-step method. 

Phase-transfer catalysis is another modern synthetic method that is currently receiving much attention. This method tends to have several advantages over traditional methods, such as higher yields, the requirement of milder reaction conditions, simplicity and the use of relatively inexpensive reagents. 

A number of other sulphoxide reduction reactions bear mentioning. The first, due to Marchelli and coworkers , is a very simple procedure whereby the sulphoxide is refluxed with t-butyl bromide and chloroform. A useful range of sulphoxides was studied and distillation of the reaction mixture (or percolation through a column of silica gel) gave pure sulphides in yields of > 90%. The procedure is appealing because of its experimental simplicity, and its use of a relatively inexpensive reagent. It may not be very successful with sterically hindered sulphoxides and the authors do not comment on this possibility. The mechanism of this reduction reaction is akin to that of BBrj (cf. Section II.A.3), except that the bromine trap is provided by a second mole of t-butyl bromide, as shown in equation (13) ... 

In order to avoid the use of a rather expensive and potentially dangerous borane complex, Bolm et al. have developed an improved procedure for the borane reduction of ketones, which involved two inexpensive reagents namely NaBH4 and TMSCI. The reduction of a series of ketones was examined applying these novel reaction conditions and the same p-hydroxy sulfoximine ligand to that described above (Scheme 10.56). For most ketones, both the level of asymmetric induction and the yield compared favorably to the precedent results. 

Based on this information the preparation of enone was examined from the unhalogenated (VIII)(X=H). Deprotonation can be performed with n-butyl lithium in THF at 0-5 °C followed by treatment with 3-ethoxy cyclohexen-l-one, followed by an acid quench provides the same enone (XI). This deprotonation also avoids the cryogenic conditions required to prepare enone (XI) when the bromo analog is used. Pyridinium tribromide used for aromatization of enone (XI) to biaryl phenol (X) is an inexpensive reagents ( 80/kg). 

A great number of natural compounds have been employed as chiral starting materials for asymmetric syntheses. Table 1-2 classifies such inexpensive reagents. 

The Sharpless epoxidation is a popular laboratory process that is both enantioselective and catalytic in nature. Not only does it employ inexpensive reagents and involve various important substrates (allylic alcohols) and products (epoxides) in organic synthesis, but it also demonstrates unusually wide applicability because of its insensitivity to many aspects of substrate structure. Selection of the proper chirality in the starting tartrate esters and proper geometry of the allylic alcohols allows one to establish both the chirality and relative configuration of the product (Fig. 4-1). 

The procedure described above provides a simple, general method for the selective, differential protection of both symmetrical and unsymmetrically substituted 1,3-diols using readily available, inexpensive reagents.3 Additional examples are summarized in the Table.3... 

However, only common and inexpensive reagents are used. They are rapid and do not require ai r expensive or sophisticated apparatus, in contrast with chromatographic methods. So, the proposed methods can be used for the routine analysis of caffeine in energy drinks. 

In this context, Czekelius and Carreira have recently documented a convenient heavy-metal-free transformation of optically active nitroalkanes 12 to chiral aldoximes 13 at room temperature by employing inexpensive reagents benzyl bromide, KOH and 5 mol% n-BU4NI (Scheme 14). This provides an environmentally friendly reaction that excludes the potential contamination of the products by metal impurities. 

Studies by the submitters have indicated that the procedure reported here is the preferred method for the preparation of bicyclo[3.2.1]octan-3-one. It employs readily available, inexpensive reagents, and the overall yield is good. In addition, the method can be used for the synthesis of the difficultly accessible next higher homologues of bicyclo[2.2.2]oct-2-ene as well as for derivatives of norbornene. Bicyclo[3.2.2]nonan-3-one and l-methylbicyclo[3.2.1]octan-3-one have been prepared by a similar route6 in 60% and 47% yields, respectively (based on adduct). However, the preferred procedure for the formation of the dichlorocarbene adduct of bicyclo[2.2.2]oct-2-ene is that of Seyferth using phenyltrichloromethylmercury. Even in this case the overall yield is moderate (37%). 

The oxidation of JV,7V -dialkylthioureas to the corresponding carbodiimides can also be accomplished in excellent yields by alkaline hypochlorites below 0°C [15, 16, 62-64], The use of excess hypochlorite converts the sulfur into sulfate ion. This process has the main advantage of using inexpensive reagents and thus can be applied to the large-scale production of carbodiimides (Eq. 20). 

This reaction is easily controlled, uses an inexpensive reagent, and gives benign products that are easily disposable. The method also shows promise as a means of converting inert saturated fluorocarbons into more reactive fiuoroalkenes or fluoroarenes for use in syntheses. 

A t-butyl bromide (iodide)/DMSO system was used by Olah [49] as a mild, inexpensive reagent to cleave dithiolanes under neutral non-aqueous conditions. 

The procedure reported here involves a one-pot reaction of the inexpensive reagent K[FeH(CO)4], which is readily available from Fe(CO)s, with a stoichiometric quantity of a phosphane in a protic medium. It affords the complexes Fe(CO)2(PR3)3 or Fe(CO)2[P(OR)3]3 in fair to high yields using tributylphosphine, dimethylphenylphosphine, and trimethyl, triethyl, and... 

The synthesis required only simple, inexpensive reagents. 

The second-generation synthesis of (S,S)-TaDiAS 1 is summarized in Scheme 6.1 [16], This process requires only common and inexpensive reagents under operationally simple reaction conditions. When using the first-generation synthesis (a five-step process from diethyl tartrate) [4a] or the second-generation synthesis (a four-step process from tartaric acid), a variety of catalysts with versatility on the acetal moieties (R1 and R2) and aromatic parts (Ar) were synthesized (over 100 derivatives) [18]. A large-scale reaction (>20g) can also be performed with the same efficiency. 

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