Carbocyclic synthesis medium-sized-ring

A highly efficient method for the synthesis of medium-sized rings (examples of 17-, 15-, 10- and 5-membered carbocycles, lactones and lactams) without high-dilu-tion conditions was developed by Trost et al. for example, precursor 204 with a palladium catalyst led to an E-Z mixture of 205 in 86% yield, and subsequent hydrogenation then provided the 10-membered lactam ring 206 in 85% yield (Scheme 15.66) [132],... 

A common use of the Cope rearrangement is the synthesis of medium-sized rings, which are present in a variety of natural products. One example is the synthesis of the carbocyclic skeleton of the fungal diterpenoid vinigrol, a compound possessing a variety of potential medicinal uses. Sodium hydride was found to be preferential to potassium hydride in promoting the anionic oxy-Cope rearrangement of 139 to provide 140. An... 

Medium sized carbocycle synthesis Ring contracting [1,2]-Wittig rearrangement Yadav and Ravishankar have demonstrated that the Wittig rearrangement of the cyclic substrate 32 is useful for the construction of the taxane skeleton 33, albeit in low yield (equation 17). ... 

The synthesis of medium-sized carbocyclic and heterocyclic rings by ring expansion reactions has been reviewed by Roxburgh <93TI0749>. In general, this section covers work not discussed by Roxburgh, except where particularly important or illustrative reactions are featured. 

Martin and co-workers applied a ring-closing metathesis strategy in the synthesis of medium-size carbocycles fused to butyrolactones/ Fused butyrolactones are ubiquitous in nature and play an important role in the... 

The most prominent and most successful compound classes in this respect are arguably VCPs and MCPs. The ring-expanding annulations of these substrates provide an opportunity for the synthesis of various medium-sized carbocyclic ring systems. However, the number of examples of asymmetric reactions remains relatively low. Their application in asymmetric catalytic processes is the next challenge to render cyclopropane ring opening more useful and fruitful. 

Synthesis of Natural Products Containing Medium-size Carbocycles by Ring-closing Alkene Metathesis... 

This chapter deals with the synthesis of naturally occurring molecules (or related models) and focuses on the construction of medium size carbocycles by ring-closing metathesis (RCM). We have arbitrarily chosen to organize this chapter by increasing ring size. Strategic aspects and potential problems are discussed. 

From a synthetic point of view, the titanium-induced mframolecular cyclization of dicarbonyl compounds is especially attractive in that carbocyclic rings of all sizes may be prepared in good yields, competitive with those obtained using the Dieckmann and acyloin cyclization methods. The synthesis of medium- and large-ring cycloalkenes by the McMurry reaction requires high-dilution conditions (< 0.0 IM) to repress intermol-ecular polymerization. ... 

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