title: Concerning the 1,5-stereocontrol in tin(IV) chloride promoted reactions of 4- and 5-alkoxyalk-2-enylstannanes: trapping intermediate allyltin trichlorides using phenyllithium.
abstract: Transmetallation of the 5-benzyloxy-4-methylpent-2-en-1-yl(tributyl)- and -(triphenyl)stannanes 1 and 8 using tin(iv) chloride generates an allyltin trichloride that reacts with aldehydes to give (Z)-1,5-anti-6-benzyloxy-5-methylhex-3-en-1-ols 2. The allyltin trichloride believed to be the key intermediate in these reactions has been trapped by phenyllithium to give anti-5-benzyloxy-4-methylpent-1-en-3-yl(triphenyl)stannane 9. Transmetallation of this anti-5-benzyloxy-4-methylpent-1-en-3-yl(triphenyl)stannane 9 generated an allyltin trichloride that reacted with aldehydes to give the (Z)-1,5-syn-6-benzyloxy-5-methylhex-3-en-1-ols 23 and was trapped by phenyllithium to give syn-5-benzyloxy-4-methylpent-1-en-3-yl(triphenyl)stannane 24. Similar stereoselectivity was observed for tin(iv) chloride promoted reactions of this syn-5-benzyloxy-4-methylpent-1-en-3-yl(triphenyl)stannane 24 with aldehydes and with phenyllithium. The allyltin trichlorides generated by transmetallation of 4-hydroxy- and 4-benzyloxy-pent-2-enyl(triphenyl)stannanes 34 and 35 were similarly trapped by phenyllithium to give 4-hydroxy- and 4-benzyloxy-pent-1-en-3-ylstannanes 36 and 37 whose configurations were established by correlation with known compounds. This work confirmed the configurations of the intermediate allyltin trichlorides involved in tin(iv) chloride promoted reactions of 4- and 5-alkoxypent-2-enylstannanes with aldehydes and showed that the high levels of remote stereocontrol were due mainly to kinetically controlled transmetallation. A fuller mechanistic scheme is proposed for the reactions in the 5-benzyloxy-4-methylpent-2-enylstannane series together with relevant (119)Sn NMR data.
authors.affiliation: The School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Lindsay A
authors.initials: LA
authors.lastname: Hobson
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Thomas
mesh_terms: D018360:Crystallography, X-Ray; D000441:Hexanols / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D009947:Organotin Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D017971:Tin Compounds / Q000737:chemistry*
chemical_list: D000441:Hexanols; D009942:Organometallic Compounds; D009947:Organotin Compounds; D017971:Tin Compounds; C450681:phenyllithium; C023599:stannous chloride