4.4.32.14 Allenylsilanes (Update 2020)

AbstractThis review is an update to the earlier Science of Synthesis coverage of the synthesis of allenylsilanes (Section 4.4.32). It covers the literature published between 2000 and 2020.The SN2 substitution of propargylic electrophiles (alcohols, oxiranes, carboxylates, sulfonates, phosphates, halides, etc.) is the most frequently used synthetic pathway to allenylsilanes. Hereby, the silyl group is either already bound to the propargylic substrate, or it is introduced using a suitable silyl nucleophile (silylcuprate, silylboronate, etc.). These methods often take advantage of transition-metal (palladium, rhodium, copper, gold, etc.) catalysis. Alternatively, propargylic nucleophiles (boranes, silanes, stannanes) are reacted with suitable electrophiles. Many of these methods can be applied to the diastereo- and/or enantioselective synthesis of allenylsilanes by using stereochemically defined starting materials or suitable chiral ligands. It is also very useful to start with allenes and convert them into allenylsilanes by deprotonation and trapping with silyl electrophiles, or by transition-metal-catalyzed coupling reactions. Conjugated ynones, enynes, and dienes also represent important classes of starting materials for the synthesis of allenylsilanes by different types of addition reactions. Finally, highly reactive substrates and reagents (silylketenes, diazo compounds, cyclopropanes, and cyclopropenes) can be readily transformed into silylallenes by alkenation, insertion, or ring-opening reactions.