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The trans‐addition of intermetallic σ‐bonds (E−E′; E E'=Si, B, Se, P, Sn, etc.) across alkynes has emerged as an exceptionally atom‐economical means of constructing multi‐substituted alkenes, which readily transform into densely functionalized and biologically active compounds. Compared to the widely studied cis‐E−E' additions, trans‐E−E' additions remain a more challenging and underdeveloped area. In this article, recent advances in trans‐E−E' additions are summarized, encompassing various interelement compounds such as Si−Si, B−B, Si−B, P−B, Se−B, and B−Sn. We aim to provide a deeper understanding of trans‐E−E' additions and facilitate the further development of synthetic methodologies and applications of vicinally trans‐bismetallated alkenes. [ABSTRACT FROM AUTHOR]

Propargyl alcohols, on treatment with MHMDS (M=Na, K), B2(pin)2, an acid chloride and a palladium/copper co‐catalyst system, undergo a reaction cascade comprised of trans‐diboration, regioselective acylation, cyclization and dehydration to give trisubstituted furylboronic acid pinacol ester derivatives in good yields; subsequent Suzuki coupling allows a fourth substituent of choice to be introduced and hence tetrasubstituted (arylated) furans to be formed. In terms of modularity, the method seems unrivaled, not least because each product can be attained by two orthogonal but convergent ways ("diagonal split"). This asset is illustrated by the "serial" formation of a "library" of all twelve possible furan isomers that result from systematic permutation of four different substituents about the heterocyclic core. [ABSTRACT FROM AUTHOR]

The hydroboration of internal alkynes with pinacolborane as the reagent catalyzed by [Cp*RuCl]4 results in good to excellent levels of regio‐ as well as stereoselectivity, provided that the triple bond bears one linear and one singly‐branched substituent. In such cases, the reaction follows an unusual trans‐addition mode and places the boron entity distal to the branching point. The resulting alkenyl boronates, which are difficult to make otherwise, can be engaged in numerous enabling downstream processes. [ABSTRACT FROM AUTHOR]

Abstract: A new strategy for the three‐component addition of halide anions and acetylenes to donor–acceptor cyclopropanes (DACs) is presented. This reaction, which occurs with high E selectivity, is promoted by gallium(III) salts and based on the 1,2‐zwitterionic reactivity of DACs. It opens up a new group of processes involving DACs. The reaction occurs readily with a broad range of substrates and is tolerant of various functional groups. This methodology makes it possible to assemble highly functionalized vinyl halides, which are very convenient building blocks in organic synthesis. A possible mechanism of this reaction and its stereochemical aspects are discussed in detail. [ABSTRACT FROM AUTHOR]

The known procedures for the conversion of alkenylstannanes into the corresponding fluoroalkenes suffer from largely variable yields and a limited compatibility with functional groups; most notably, protodestannation becomes a serious issue whenever protic sites are present in the substrate. Outlined in this paper is a convenient alternative with a much improved application profile, which is largely unperturbed by free alcohols and amides of all sorts. Key to success is the use of F-TEDA-PF6 in combination with non-hygroscopic and bench-stable silver phosphinate (AgOP(O)Ph2) that acts as an essentially neutral, non-nucleophilic promotor and effective tin-scavenger at the same time. This new method opens many opportunities for late-stage fluorination of elaborate compounds far beyond the scope of the literature procedures, as witnessed by the preparation of a fluorinated macrolide antibiotic, a fluorinated prostaglandin derivative, and a set of fluorinated amino acid surrogates and peptide isosteres. [ABSTRACT FROM AUTHOR]

Regel missachtet: Die Stereochemie einer Hydroborierung wird gewöhnlich durch suprafacialen Angriff von Wasserstoff und Bor an der gleichen π ‐ Seite eines Substrats bestimmt. Diese grundlegende Regel der cis ‐ Addition kann jetzt für interne Alkine mit [Cp*Ru(MeCN)3]PF6 (Cp*=η5 ‐ C5Me5) als Katalysator gebrochen werden. Die daraus resultierende trans ‐ selektive Hydroborierung ermöglicht die Synthese von E ‐ konfigurierten Alkenylbor ‐ Derivaten. [ABSTRACT FROM AUTHOR]