Sulfoxide-mediated Umpolung of alkali halide salts

A new protocol for the direct two-electron oxidative Umpolung of alkali halide salts is reported. This procedure, relying on the use of a commercially available sulfoxide as the oxidant, allows the electrophilic halogenation of carbonyl compounds as well as halolactonisation reactions to proceed from the corresponding sodium salts, at room temperature and under mild conditions

Palladium-Catalyzed Allylic Substitution at Four-Membered-Ring Systems: Formation of η¹-Allyl Complexes and Electrocyclic Ring Opening

Caught in the act: A series of unique η1-allyl palladium complexes of four-membered cyclic systems bearing β-hydrogens were prepared (see structure). Their unusual structure, reactivity, and unprecedented propensity for undergoing pericyclic reactions were uncovered

Direct Domino Synthesis of Azido-Dienoic Acids: Potential Linker Units

We report an atom-economical domino synthesis of functionalized and stereodefined dienes. This method hinges on an allylic alkylation–electrocyclic ring-opening sequence and allows direct access to doubly vinylogous azido-dienoic acids bearing challenging substitution patterns. This class of compounds re­presents useful linkers in chemical biology by virtue of the ortho­gonality between the azido and carboxylic acid moieties

An Atom-Economical and Stereoselective Domino Synthesis of Functionalised Dienes

Open sesame: A direct synthesis of functionalised and stereodefined dienes, relying on a domino allylic alkylation/electrocyclic ring-opening sequence, is reported. This method allows concise access to doubly vinylogous esters. A further systematic study of ring-opening rates of carbon-substituted cyclobutenes allowed the design of substrates amenable to sequential pericyclic reactions

Totalsynthese und Strukturrevision der Piperarborenine: Photochemie trifft auf C-H-Aktivierung

Aktivieren und Wiederholen: Die Aktivierung von C(sp3)-H-Bindungen ist eine attraktive Umwandlung, da zügig molekulare Komplexität auf Kosten der einfachsten und am leichtesten zugänglichen organischen Bindung aufgebaut wird. Kürzliche Beiträge nutzten diesen Ansatz zur Kupplung an kleine Kohlenstoffringe, z. B. zur sequenziellen C-H-Aktivierung in der eleganten Totalsynthese der Piperarborenine (siehe Schema)

Total Synthesis and Structural Revision of the Piperarborenines: When Photochemistry Meets C-H Activation

Activate and reiterate: The activation of C(sp3)H bonds is a highly desirable transformation because molecular complexity can be increased at the expense of the most simple and readily available organic linkage. In recent contributions this approach was used for coupling reactions with small all-carbon rings, as exemplified by the sequential CH activation steps in an elegant total synthesis of the piperarborenines (see scheme; DG=directing group)

The Redox-Neutral Approach to C-H Functionalization

The direct functionalization of C[BOND]H bonds is an attractive strategy in organic synthesis. Although several advances have been made in this area, the selective activation of inert sp3 C[BOND]H bonds remains a daunting challenge. Recently, a new type of sp3 C[BOND]H activation mode through internal hydride transfer has demonstrated the potential to activate remote sp3 C[BOND]H linkages in an atom-economic manner. This Minireview attempts to classify recent advances in this area including the transition to non-activated sp3 C[BOND]H bonds and asymmetric hydride transfers