Functional groups, versatility

Functional Group Versatility Claisen Rearrangement Reaction Variants... 

Organic compounds are grouped into families according to the functional groups they contain Two of the most important families are alcohols and alkyl halides Alco hols and alkyl halides are especially useful because they are versatile starting materials for preparing numerous other families Indeed alcohols or alkyl halides—often both— will appear m virtually all of the remaining chapters of this text... 

The versatility of lithium aluminum hydride permits synthesis of alkyl, alkenyl, and arylsilanes. Silanes containing functional groups, such as chloro, amino, and alkoxyl in the organic substituents, can also be prepared. Mixed compounds containing both SiCl and SiH cannot be prepared from organopolyhalosilanes using lithium aluminum hydride. Reduction is invariably complete. 

Core Functional Group. A member of the most simple, fundamental, and synthetically versatile class of functional groups, such as carbonyl, hydroxyl, olefinic, acetylenic, and amino groups. 

Alcohols are versatile starting materials for the preparation of a variety of organic functional groups. Several reactions of alcohols have aheady been seen in earlier chapters and are summarized in Table 15.2. The remaining sections of this chapter add to the list. 

The Wolff rearrangement is a versatile reaction R can be alkyl as well as aryl most functional groups do not interfere. The generally mild reaction conditions permit an application to sensitive substrates. 

Many pharmacologically active compounds have been synthesized using 5-bromoisoquinoline or 5-bromo-8-nitroisoquinoline as building blocks.6 7 8 9 10 11 The haloaromatics participate in transition-metal couplings 81012 and Grignard reactions. The readily reduced nitro group of 5-bromo-8-nitroisoquinoline provides access to an aromatic amine, one of the most versatile functional groups. In addition to N-alkylation, TV-acylation and diazotiation, the amine may be utilized to direct electrophiles into the orthoposition. 

The versatility, predictability and functional-group tolerance of free radical methodology has led to the gradual emergence of homolytic reactions in the armory of synthetic chemistry. Tin hydrides have been successfully employed in radical chemistry for the last 40 years however, there are drawbacks associated with tin-based chemistry. Organotin residues are notoriously difficult to remove from desired end products, and this, coupled with the fact that many organotin compounds are neurotoxins, makes techniques using tin inappro-... 

These processes have flourished, mainly due to their selectivity and versatility, to the point where cross-coupling chemistry is often the initial thinking of organic chemists in synthetic and retro-synthetic approaches [2]. In fact, nowadays it is difficult to find a contribution in fine chemical or natural product synthesis where these molecular assembly tools are not employed. This is often due to the simple preparation and handling of the reaction partners as well as their relative compatibility with several functional groups. 

The Stille reaction has developed as a popular protocol for the formation of C-C bonds due to the air- and moisture-stability as well as functional group compatibility of organotin compounds. Together with the Suzuki-Miyaura coupling it is one of the most powerful methods for the synthesis of molecules containing unsymmetrical biaryl moieties. However, despite its efficiency, this versatile reaction has slowly been displaced by other procedures that avoid the use of highly toxic organostannanes. 

Because they are readily available from natural sources in enantiomerically pure form, carbohydrates are very useful starting materials for the synthesis of other enantiomerically pure substances. However, the high number of similar functional groups present in the carbohydrates requires versatile techniques for protection and deprotection. Show how appropriate manipulation of protecting groups and other selective reactions could be employed to effect the following transformations. 

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