424789-08-2Relevant academic research and scientific papers
Enantioselective Synthesis of cis-2,6-Disubstituted-4-methylene Tetrahydropyrans via Chromium Catalysis?
Bai, Jing,Chen, Bin,Zhang, Guozhu
, p. 1642 - 1646 (2020)
Enantioenriched 2,6-disubstituted 4-methylene tetrahydropyrans have been obtained via a two-step sequence consisting of a highly enantioselective chromium-catalyzed carbonyl 2-(trimethylsilyl methyl)allylation and Prins cyclization. Commercially available (2-(chloromethyl)allyl)trimethylsilane serves as the bifunctional linchpin to combine two aldehydes to assemble the 2,6-disubstituted pyrans. A variety of functional groups are compatible under the mild reaction conditions. The synthetic utility of this methodology was demonstrated by the asymmetric synthesis of 16 examples of homoallylic alcohol and 8 examples of 2,6-disubstituted 4-methylene tetrahydropyrans, including an advanced intermediate which could be transformed to natural product centrolobine via a known procedure.
Sequential catalytic asymmetric allylic transfer reaction: Enantioselective and diastereoselective construction of tetrahydropyran units
Yu, Chan-Mo,Lee, Jae-Young,So, Byungran,Hong, Junghyun
, p. 161 - 163 (2007/10/03)
Useful tetrahydropyran units such as 3 can be prepared with high diastereoselectivity (d.r. > 30:1). A key step is the catalytic asymmetric allyl-transfer reaction from 1 to achiral aldehydes catalyzed by [{(R) binol}TiIV{OCH(CF3)2}2] to give 2 (90-97% ee). A second allyl-transfer reaction from 2 to a carbonyl compound leads to 3. binol = 2,2′-binaphthol.
