77180-30-4Relevant academic research and scientific papers
Stereoselective Cyclizations and Rearrangements in Vinyl Radicals Promoted by Regioselective Sulfanyl Radical Addition to Enynes
Montevecchi, Pier Carlo,Navacchia, Maria Luisa
, p. 5600 - 5607 (1997)
Regioselective radical addition of 4-cyanotoluenethiol (1a) to enynes 3-6 leads to vinyl radicals 7-10 that can undergo five- or six-membered cyclization onto styrene or terminal double bonds in competition with 5-exo cyclization onto the aryl ring. The latter affords spiro-cyclohexadienyl radical intermediates which can either be trapped by 2-cyanoisopropyl radicals or give 1,4-aryl migration products. Regioselective radical addition of phenethanethiol (1b) to enynes 3-6 gives radicals 11-14 which undergo five- or six-membered cyclization onto the alkene double bond; the stereoelectronically disfavored 6-exo cyclization can compete with intermolecular hydrogen abstraction and (to a small extent) with 1,5-hydrogen migration. The 5- and 6-(π-exo)exo cyclization of vinyl radicals 7, 9, 11-13 is highly stereoselective and exclusively or predominately affords products deriving from the (Z)-isomers. Stereochemical evidence indicates that the six-membered endo-cyclization products 30 and 50 could derive from a direct 6-endo cyclization of (E)-radicals (E)-10 and (E)-14 rather than from a 5-exo cyclization/ring expansion process. Sulfanyl radical addition to enynes 3-5 is highly regioselective to the terminal triple bond. In contrast, reaction of thiols 1a,b with enyne 6 leads to products deriving from sulfanyl radical addition to both the CC triple and double bond. This behavior is accounted for by assuming that sulfanyl radical addition to the alkyne triple bond is not reversible, while the addition to the alkene double bond is. Vinyl radical 10 affords product 33 by a rare 1,4-hydrogen migration/fragmentation process.
Enantioselective Palladium-Catalyzed Hydrophosphinylation of Allenes with Phosphine Oxides: Access to Chiral Allylic Phosphine Oxides
Wang, Jun,Yang, Zhiping
supporting information, p. 27288 - 27292 (2021/11/17)
A Pd-catalyzed hydrophosphinylation of alkyl and aryl-oxyallenes with phosphine oxides has been developed for the efficient and rapid construction of a family of chiral allylic phosphine oxides with a diverse range of functional groups. This methodology was further applied in the facile construction of chiral 2H-chromene and later stage functionalization of cholesterol.
