Direct Syn Addition of Two Silicon Atoms to a C≡C Triple Bond by Si−Si Bond Activation: Access to Reactive Disilylated Olefins

Abstract

A catalytic intramolecular silapalladation of alkynes affords, in good yields and stereoselectively, syn‐disilylated heterocycles of different chemical structure and size. When applied to silylethers, this reaction leads to vinylic silanols that undergo a rhodium‐catalyzed addition to activated olefins, providing the oxa‐Heck or oxa‐Michael products, depending on the reaction conditions.

Synthesis of N‐Heterocycles‐Fused Azasilines by Palladium‐Catalyzed Si‐Si Bond Activation

“…In a previous paper, we have shown that palladium complexes allow a selective intramolecular silapalladation of aryl alkynes, affording a set of silylacyclic compounds. In this work, we describe the extension of these results to heterocyclic disilane substrates still using palladium catalysts (Scheme ).…”

“…Several routes to access pyridyl disilanes 5 from commercially available amino/hydroxy‐pyridines were evaluated. The simple three‐step (bromination ‐ disilane introduction ‐ N / O ‐propargylation) procedure used previously was examined first. Unfortunately, the early introduction of the disilane appendage revealed difficulties with amino‐ or hydroxy‐pyridine.…”

“…With disilapyridines 5 and 8 in hand, we first examined the reactivity resorting to the previously optimized conditions ( i. e . 5 % Pd(dba) 2 +10 % P(OEt) 3 , 3 h at reflux of xylenes) . Results in Scheme show that the cyclisation takes place in good to excellent yields and with total stereo‐ and regioselectivities ( syn ‐addition, 6‐ exo ‐ dig cyclisation).…”

“…Over the past decade, research in our group has opened new strategies and methods to access at silylated heterocycles through cyclization reactions . Notably, we have found that intramolecular rearrangement triggered by a silapalladation reaction can be easily carried out in high regio‐ and stereoselectivities using palladium – phosphite complex in xylenes . We now report results, combining our previous works on intramolecular carbometallation reactions (lithium, nickel) and the synthesis of silylheterocycles, in an effort to selectively access valuable nitrogen heterocycles scaffolds, while increasing molecular diversity.…”