Synthesis of Diynes and Tetraynes from in Situ Desilylation/Dimerization of Acetylenes
摘要:
[GRAPHICS]An efficient method for the in situ desillylation/oxidative dimerization of (trialkylsilyl)acetylenes is described. This protocol avoids the complications encountered with sensitive diynes by eliminating the deprotection and isolation steps. Various aromatic and alkyl diynes and tetraynes can be synthesized in a straightforward manner in good yields (82-99%) from TIPS-protected acetylenes. This method facilitates the efficient synthesis of novel tetrayne-bridged acetylenic cyclophanes 6 and 7 in a direct manner.
Cyclopropenation of internal alkynylsilanes and diazoacetates catalyzed by copper(<scp>i</scp>) N-heterocyclic carbene complexes
作者:Thomas J. Thomas、Benjamin A. Merritt、Betsegaw E. Lemma、Adina M. McKoy、Tri Nguyen、Andrew K. Swenson、Jeffrey L. Mills、Michael G. Coleman
DOI:10.1039/c5ob02259b
日期:——
Copper(I) N-heterocycliccarbene (CuNHC) complexes are more catalytically active than traditional transition metal salts for the cyclopropenation of internal alkynylsilanes and diazoacetate compounds. A series of 1,2,3-trisubstituted and 1,2,3,3-tetrasubstituted cyclopropenylsilane compounds were isolated in good overall yields. An interesting regioselective and chemodivergent reaction pathway was
silyl alkynoate in N,N-dimethylformamide (DMF) at 80 °C in the presence of catalytic amounts of CuCl and PCy3 produced the corresponding alkynylsilane in excellent yield. The copper-catalyzed decarboxylation proceeded smoothly with low catalyst loadings (0.5 mol % of CuCl and 1.0 mol % of PCy3) under mild reaction conditions and is easily scalable to gram quantities.
Geometric
<i>E</i>
→
<i>Z</i>
Isomerisation of Alkenyl Silanes by Selective Energy Transfer Catalysis: Stereodivergent Synthesis of Triarylethylenes via a Formal
<i>anti</i>
‐Metallometallation
作者:Svenja I. Faßbender、John J. Molloy、Christian Mück‐Lichtenfeld、Ryan Gilmour
DOI:10.1002/anie.201910169
日期:2019.12.16
An efficient geometrical E→Z isomerisation of alkenyl silanes is disclosed via selective energy transfer using an inexpensive organic sensitiser. Characterised by operational simplicity, short reaction times (2 h), and broad substrate tolerance, the reaction displays high selectivity for trisubstituted systems (Z/E up to 95:5). In contrast to thermal activation, directionality results from deconjugation
A highly selective hydrogenation of alkynesusing an air-stable and readily available manganese catalyst has been achieved. The reaction proceeds under mild reaction conditions and tolerates various functional groups, resulting in (Z)-alkenes and allylic alcohols in high yields. Mechanistic experiments suggest that the reaction proceeds via a bifunctional activation involving metal–ligand cooperativity
Palladium-catalyzed denitrative Sonogashira-type cross-coupling of nitrobenzenes with terminal alkynes
作者:Boya Feng、Yudong Yang、Jingsong You
DOI:10.1039/c9cc08663c
日期:——
Described herein is a palladium-catalyzedcross-couplingreaction between nitroarenes and terminal alkynes, offering a facile method for C(sp2)-C(sp) bond formation. The utility of this protocol has been proven by the construction of polycyclic aromatic hydrocarbons (PAHs) and orthogonal cross-coupling.