Protection reactions types

Among several types of reactors investigated, the microstructured reactor was successfully applied to the synthesis of a pharmaceutical intermediate via a fast exothermic Boc protecting reaction step. The reaction temperature was isothermally controlled at 15°C. By using the microstructured reactor the heat of reaction was completely removed so that virtually no byproducts were produced during the reaction. Conversions as high as 96% were achieved. The micro-reactor operation can be compared with other reactors, however, which need to be operated at 0°C or -20°C to avoid side reactions. 

The protecting reaction of the enamino pyrrolidinone with t-butoxycarbonyl anhydride was carried out by mixing 4-(N-/-butoxycarbonyl)-4-aminomethylene-pyirolidin-3-one (Boc-AMP) with 1.2 molar equivalents of t-butoxycarbonyl anhydride (/-BoczO) to make l-(N-f-butoxycarbonyl)-4-(N-t-butoxycarbonyl)-ammomethylene-pyrrolidin-3-one (B0C2-AMP). Several types of reactors, including batch reactors, a continuous stirred tank reactor (CSTR),... 

Type of reaction protection Reaction condition solid-state... 

In reviewing the chemical diversity systems outlined in the previous chapter, the utility of applying a variety of different reaction types productively on solid phase has become apparent. Combinatorial chemists must develop the skills to maintain a high level of flexibility, with respect to the pathways accessible in the solid-phase mode of operation. The diversity of building blocks, available in principle to everyone, needs to be complemented by a diversity of methods on how to link them. This skill base is available only to the advanced laboratories in the field. Furthermore, the know-how in the area of protecting group chemistry needs extension into the issues concerning solid phase linkers and the actual solid-phase matrices. 

A ring expansion by two carbon atoms was discovered on heating (Z)-l-vinyl-cyclonon-3-en-l-yl-trimethylsilyl ether (V/62), Scheme V/10 [31] [32], Two types of trimethylsiloxy enol ethers were observed, each formed by a [1.3] or a [3.3] sigmatropic shift which, after hydrolysis, gave the ketones V/63, V/64, and V/65. The protection of the tertiary alcohol function is not necessary, if the reaction is done in the presence of potassium hydride [33] [34]. The reaction proceeds when the cyclic 1-vinyl alcohols have either a double bond or a benzo group at the 3-position. Other examples of this reaction type are given in Scheme V/10. 

The necessity to protect hydroxyl groups selectively is frequently encountered in a total synthesis. Therefore an all cases scenario set of reactions has been created for this important functionality. Some of the more commonly encountered methods are summarized in Scheme 2.90. The list of protected compounds includes such derivatives of alcohols as esters (201-203), acetals (204, 205), ethers (206-209), and organosilicon ethers (210, 21The methods used to introduce these protecting groups vary tremendously. All of them actually represent different versions of the same reaction type, electrophilic substitution of the hydrogen of the hydroxyl group. The main differences are in the reaction conditions, e.g. acidic, neutral, or basic, required to form these derivatives. The... 

Type of reaction Protection Reaction condition solvent-free... 

Type of reaction protection Reaction condition solvent-free Keywords A-Boc protection, amine, iodine... 

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