Each reaction is delineated by its detailed step-by-step, electron-pushing mechanism, supplemented with the original and the latest references, especially review articles. This approach was attractive because Marinovic reported a two-step synthesis of dione 5 in 1983. Introduction Martin Sulfurane, a diphenylsulfur compound, has been a versatile reagent in organic synthesis since the 1970s. Oxidation of 13 with 8 equiv of SeO 2 in dioxane at 140 °C in a microwave reactor for 30 min afforded allylic alcohol 17 in only 27% yield. Gegenuber der zweiten Auflage wird der Platz effektiver genutzt.
The structures of 7 and 8 could not be assigned at this point so both compounds were carried on. The Martin's sulfurane is a very powerful dehydration reagent and can be applied to efficiently dehydrate alcohols under very mild conditions. © 2013 The American Chemical Society and American Society of Pharmacognosy. Although macrocarpal C is of biological interest, its isolation in pure form is difficult to achieve. Radical cyclization of this mixture of 7 and 8 with n-Bu 3SnH in benzene at reflux afforded the tricyclic diones 5 and 9 in 85% yield, again with unspecified stereochemistry. Description: 1 online resource xxii, 621 pages : illustrations Contents: Alder ene reaction.
Three Dimensional Representations and Molecular Structures of 5 and 9 Established by X-ray Structure Determination. Figure 1 The Sulfurane is reactive towards active hydrogen compounds and is one of the reagents of choice for a class of reactions including dehydration, amide cleavage, epoxide formation, sulfinimine synthesis, oxidation and coupling. Oxidation of alkene 13 with only 3 equiv of SeO 2 in dioxane at 110 °C in a microwave reactor for only 10 min afforded allylic alcohol 17 in 83% yield and enone 2 in 7% yield. For o-substituted phenols, initial incorporation of a benzotriazole on the phenol oxygen was required. A range of functional groups as well as different cyclic and bicyclic frameworks were found to be compatible with the reaction conditions. Acid catalyzed cyclization afforded 12 90% , which was elaborated to 13 as previously described.
Unlike other books on name reactions in organic chemistry, Name Reactions, A Collection of Detailed Reaction Mechanisms and Synthetic Applications focuses on their mechanisms. This resulted in the formation of an inseparable 1:1 mixture of 4 and 11 in 90% yield see. The format change has doubled the space to accommodate at least two to three real case applications in synthesis for each name reaction. The references are updated to 2009. L-Selectride reduction of dione 5 should provide the bis axial alcohol 4 see. This three-step sequence converts tricyclic dione 5 to tetracyclic alkene 13 in 63% overall yield, but diols 4 and 11 cannot be characterized.
Several dehydration process have been discussed using Martin's sulfurane. Reductive alkylation of 5-methoxy-1-tetralone 6 with 2,3-dibromopropene gave an equilibrium mixture of bicyclic diones 7 51% and 8 35%. Several new name reactions and reagents are included to reflect the state-of-the-art of organic chemistry. Similar treatment of the equatorial alcohol 12 afforded triflate 14, which did not undergo E2 elimination readily because there is no β-hydrogen anti to the triflate. The study finds that moisture must be avoided during the reaction.
A mechanism involving the intermediacy of a sulfurane is proposed to account for the experimental observations. In contrast, per-fluorination, the usual way to stabilize hypervalent structures, is found to have an opposite effect here. Allylic oxidation of 13 with SeO 2 and activated MnO 2 afforded enone 2 in 85% yield, thereby completing a short formal synthesis of ± -platensimycin. The broad spectrum antibiotic platensimycin 1 see was recently isolated by a Merck group from Streptomyces platensis as part of a screening program designed to isolate inhibitors of bacterial fatty acid biosynthesis by the highly conserved condensing enzyme FabF. Martin Sulfur provides gathering, marketing, and distribution services for U. Oxidation of 13 with CrO 3·pyridine was slower, but gave the same ratio of products. Nicolaou recently reported the first synthesis of platensimycin 1 in which he prepared 2 in 10 steps and elaborated it to ± -platensimycin 1.
A useful resource for senior undergraduate and graduate students for learning and exams, but also a good reference book for all organic chemists. Once solidified, the formed sulfur is stored in open air stockpiles until ultimately reclaimed and loaded aboard dry bulk vessels bound for foreign markets. We planned to prepare 2 by dehydration of the alcohol of 3 and allylic oxidation. Therefore, it might be possible to isolate 7 in acceptable yield and convert it to 5 if the radical cyclization can be carried out without epimerization. Aus den Rezensionen zur 3. Subsequent ortholithiation and borylation gave the coupled product, again with complete stereospecificity.
Substitution of F by heavier analogs of the group did not lead to any stable oligomers. A series of six-membered rings bearing cis oriented vicinal carboxylate and sulfinate esters were treated with Grignard reagents with the intention of transforming them to β-carboalkoxy substituted sulfoxides. The equilibration of both bicyclic diones 7 and 8 and tricyclic diones 5 and 9 thus gave results close to those expected from molecular mechanics calculations. Reduction of 10 with L-Selectride afforded diol 11 contaminated with a few percent of the equatorial alcohol in 83% yield. Oxidation of alcohol 17 with activated MnO 2 provided enone 2 in 94% yield.
When isomer mixtures of sterically encumbered sulfinate esters were reacted, a single sulfoxide stereochemistry resulted. A similar sequence converted the undesired bicyclic dione 8 to tricyclic dione 9 in 81% yield. As such, the substrates possessing eclipsing carboxylate and sulfinate esters accepted two organic ligands at the carboxylate functionality and one at the sulfinyl group. L-Selectride reduction of the unhindered ketone of 5 occurred readily at -78 °C, but gave a 1:1 mixture of equatorial and axial alcohols. Eventually, we found that treatment of crude triflate 14 with either silica gel or hydrochloric acid resulted in clean elimination, possibly by an E1 mechanism, to form alkene 13 in 84% yield from 12. These bulk storage and forming facilities provide U. Addition of LiBr and then 2,3-dibromopropene effected alkylation.