Synthetic development

The chemistry of furazans and furoxans has been the subject of intensive investigations over the years. There has been been a substantial increase in synthetic manipulations of substituents attached to these ring systems. Additionally, there are a number of publications that deal with the incorporation of the heterocyclic rings into more complex molecules. It is the aim of this review to present new synthetic developments and to update reviews in the field of... 

The total synthesis of palytoxin (1) is a landmark scientific achievement. It not only extended the frontiers of target-oriented synthesis in terms of the size and complexity of the molecules, but also led to new discoveries and developments in the areas of synthetic methodology and conformational analysis. Among the most useful synthetic developments to emerge from this synthesis include the refinement of the NiCh/CrC -mediated coupling reaction between iodoolefins and aldehydes, the improvements and modifications of Suzuki s palladium-catalyzed diene synthesis, and the synthesis of A-acyl vinylogous ureas. 

The state of the synthetic art in this area, in 1979, is much more satisfactory. During the past decade, several new synthetic developments have occurred such that we are closer to the point where the limitations upon synthesis of trifluoromethyl compounds are related more to stability problems in isolated cases, and are not nearly so much due to lack of widely applicable synthetic techniques. We find ourselves, for example, in a position in 1979 where the germanium compound, Ge(CF3)4, which in the past decade, was considered by many workers to be of insufficient stability to permit isolation, has been prepared by four independent methods and is known to be stable to over 100°C. Many of these new synthetic techniques have emerged from studies conducted in our laboratory at the University of Texas and previously... 

Generally speaking, we should note that the synthetic potentials of the polycondensation approach for the preparation of protein-like copolymers are only now beginning to be explored. Nonetheless, even the first results show promising directions for future synthetic developments that can hardly be reached through the polymerization processes. 

In this section, the literature about Diels-Alder reactions will be presented in a conceptual and illustrative way. After a profound introduction dealing with the development of mechanistic understanding of the Diels-Alder reaction, some interesting recent synthetic developments and applications will be presented. The reaction types and fields of interest are structured in such a way that they can be easily linked to ongoing research from the past ten years. Special attention will be paid to the application of chiral auxiliaries and chiral Lewis acids in asymmetric Diels-Alder reactions. 

Animals fed spoiled sweet clover were prone to fatal haemorrhages. The canse was traced to the presence of dicoumarol. This compound interferes with the effects of vitamin K in blood coagulation, the blood loses its ability to clot, and minor injnries can lead to severe internal bleeding. Synthetic dicoumarol has been nsed as an oral blood anticoagnlant in the treatment of thrombosis, where the risk of blood clots becomes life threatening. It has since been snperseded by warfarin, a synthetic development based on the natnral prodnct. 

As a third group of fullerene-like systems whose synthetic development is identified as a major future challenge are structurally defined single-walled carbon nanotubes (SWNTs) with uniform helicity and length, including their covalent and non-covalent derivatives. SWNTs can be considered as elongated giant fullerenes. 

Paquette, Leo A. Recent synthetic developments in polyquinane chemistry. 

Paquette, L. A. Recent Synthetic Developments in Polyquinane Chemistry. 119, 1-158 (1984). 

As mentioned in the introduction, recent synthetic developments now allow access to the 1,2-thiazine structure via disconnection type C (Figure 23). This process can be accomplished by a Friedel-Crafts-type cyclization of sulfamoyl chlorides. The initial report of this reaction utilized a stoichometric amount of aluminium chloride promoter <19920PP463>. Recently, however, A -ethyl phenethylsulfamoyl chloride 214 was shown to undergo Friedel-Crafts cyclization to form sultam 215 with just a catalytic amount of In(OTf)3 (Equation 33) <2002SL1928>. 

Most of the recent synthetic developments in the field of radical cyclization have involved the reactions of carbon-centered radicals with alkenes and alkynes. Other useful acceptors include allenes,31 dienes30 and vinyl epoxides.32 The same methods are used for cyclizations to these acceptors as for radical additions, and the preceding chapter should be consulted for specific details on an individual method (the organization of this section parallels that of Section 4.1.6). Selection of a particular method to conduct a proposed cyclization is based on a variety of criteria, including the availability of the requisite pre-... 

Extensive synthetic developments have occurred recently in this field, primarily because of improvements in the catalysts used and the procedures for preparation of the carbenoid precursors. Consequently,... 

It is the intent of this chapter to outline the major synthetic developments of the intramolecular asymmetric Heck reaction as well as to examine the mechanistic factors that have been revealed to date that effect enantioselectivity. 

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