3-Silaazetidine Synthesized from Air-Stable Precursor

3-Silaazetidine Synthesized from Air-Stable Precursor

Author: ChemistryViews.org

Strained, small, three- or four-membered silacycles are useful in organic synthesis. In contrast, nitrogen-containing four-membered silacycles, such as 2-silaazetidine and 3-silaazetidine (pictured), are challenging to prepare and air-sensitive. This severely limits their use in synthesis.

Zhenlei Song, Sichuan University, Chengdu, China, and colleagues have prepared 3-silaazetidines in situ from air-stable precursors and used them in the synthesis of larger silaazacycles via a ring expansion. The team used precursors of the type TsNHCH2–SiR2–CH2Cl (Ts = toluenesulfonyl) with a variety of alkyl or aryl substituents at the silicon atom and converted them to the corresponding 3-silaazetidines using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) as a base. These in-situ-formed 3-silaazetidines were reacted with terminal alkynes in a palladium-catalyzed ring-expansion reaction to give 3-silatetrahydropyridines. The team used Pd(PPh3)2Cl2 as the catalyst, ZnI2 as an additive, and xylenes as the solvent.

The desired 3-silatetrahydropyridines were obtained in moderate to good yields. The precursors can be synthesized on a gram scale and the 3-silatetrahydropyridine products could be further functionalized to obtain a variety of silaazacyclic compounds. The researchers hope that access to the reactive 3-silaazetidines could allow their use in other organic syntheses.



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