The behavior of 1,n-enynes in the presence of transition metals.

The hetero Diels-Alder reaction is one of the most important methods for the synthesis of heterocycles. In this article an overview is given for the period since 1989 describing the reaction of heterobutadienes such as oxabutadienes, thiabutadienes, azabutadienes, diaazabutadienes, nitroso-alkenes and nitroalkenes as well as of heterodienophiles such as carbonyls, thiocarbonyls, imines, iminium salts, azo- and nitroso compounds. In addition, several other less common hetero Diels-Alder reactions such as cycloadditions of thiaazabutadienes, oxaazabutadienes, dioxabutadienes, dithiabutadienes, oxathiabutadienes, diazaoxabutadienes as well as the use of N-sulfinyl-phosphaalkynes and other dienophiles are mentioned. A main point of discussion is the stereoselectivity of the reactions and the preparation of enantiopure compounds either using dienes and dienophiles carrying a chiral auxiliary or employing chiral Lewis acids. A point stressed is the synthesis of natural products using hetero Diels-Alder reactions leading to carbohydrates, alkaloids, terpenes, antibiotics, mycotoxins, cytochalasans, antitumor agents and several other classes of natural products.

Hetero diels-alder reactions in organic chemistry

Most of the efforts of organic chemists have been directed to the development of creative strategies to build carbon–carbon and carbon–heteroatom bonds in a predictable and efficient manner. In this Review, we show an alternative approach where challenging molecular skeletons could be prepared through selective cleavage of carbon–carbon bonds. We demonstrate that it has the potential to be a general principle in organic synthesis for the regio-, diastereo-, and even enantioselective preparation of adducts despite the fact that CC single bonds are among the least reactive functional groups. The development of such strategies may have an impact on synthesis design and can ultimately lead to new selective and efficient processes for the utilization of simple hydrocarbons.

Selective Carbon–Carbon Bond Cleavage for the Stereoselective Synthesis of Acyclic Systems

This full account presents the background on, discovery of, and extensive insight that has been gained into the oxidative intermolecular coupling of two different carbonyl species. Optimization of this process has culminated in reliable and scalable protocols for the union of amides, imides, ketones, and oxindoles using soluble copper(II) or iron(III) salts as oxidants. Extensive mechanistic studies point to a metal-chelated single-electron-transfer process in the case of copper(II), while iron(III)-based couplings appear to proceed through a non-templated heterodimerization. This work presents the most in-depth findings on the mechanism of oxidative enolate coupling to date. The scope of oxidative enolate heterocoupling is extensive (40 examples) and has been shown to be efficient even on a large scale (gram-scale or greater). Finally, the method has been applied to the total synthesis of the unsymmetrical lignan lactone (-)-bursehernin and a medicinally important 2,3-disubstituted succinate derivative.

Intermolecular Enolate Heterocoupling: Scope, Mechanism, and Application

Enantiomerically enriched cyclopropene derivatives, the smallest possible unsaturated carbocycles, are of great synthetic interest since they serve as versatile reactive building blocks Their reactivity results from the relief of the ring strain in the small molecule They can be transformed into a wide variety of complex chiral structures and a special emphasis will be directed towards the preparation of enantiomerically enriched methylene- and alkylidenecyclopropane derivatives The ready availability of a wide range of these chiral entities now provides an excellent opportunity to discover new and unique transformations that can further enrich mainstream synthetic methodology

Enantiomerically enriched cyclopropene derivatives: versatile building blocks in asymmetric synthesis.

Oxidative Coupling of the Enolate Anion of (1R)-(+)-Verbenone with Fe(III) and Cu(II) Salts. Two Modes of Conjoining This Bicyclic Ketone across a Benzene Ring

Heteroatomic Influences on the .pi.-Facial Selectivity of Diels-Alder Cycloadditions to Dispiro[4.0.4.4]tetradeca-11,13-dienes

Generation and chemical trapping of a bis(ethano) derivative of tricyclo[3.3.0.03,7]oct-1(5)-ene. The consummate member of a series of pyramidalized alkenes

The four tetraspiro carbinols 28, 30, 41, and 43 and the three trispiro cyclohexenones 25, 38, and 53 have been synthesized and individually subjected to intramolecular oxymercuration. The three-di...

Bruce M. Branan

Papers

Oxidative Coupling of the Enolate Anion of (1R)-(+)-Verbenone with Fe(III) and Cu(II) Salts. Two Modes of Conjoining This Bicyclic Ketone across a Benzene Ring

Heteroatomic Influences on the .pi.-Facial Selectivity of Diels-Alder Cycloadditions to Dispiro[4.0.4.4]tetradeca-11,13-dienes

Generation and chemical trapping of a bis(ethano) derivative of tricyclo[3.3.0.03,7]oct-1(5)-ene. The consummate member of a series of pyramidalized alkenes

Intramolecular Oxymercuration of Stereoisomeric Cyclohexyl-Belted Poly(spirotetrahydrofuranyl) Platforms

Conformational Analysis of Poly(spirotetrahydrofuranyl)cyclohexyl Systems. The Preference of Multiple C−O Bonds for Equatorial Occupancy