title: Enantioselective synthesis of (Z)- and (E)-2-methyl-1,5-anti-pentenediols via an allene hydroboration-double-allylboration reaction sequence.
abstract: Kinetically controlled hydroboration of allenylboronate 5 followed by double allylboration with the resulting allylborane (Z)-7 gave (Z)-2-methyl-1,5-anti-pentenediols 6 in good yield and high enantioselectivity in the presence of 10% BF3·OEt2 as the catalyst in the second allylboration step. Under thermodynamically controlled isomerization conditions, (Z)-7 can readily isomerize to (E)-7. Double allylboration of representative aldehydes with allylborane (E)-7 gave (E)-2-methyl-1,5-anti-pentenediols 4 in good yield and high enantioselectivity without requiring use of the BF3·OEt2 catalyst. Thus, 2-methyl-1,5-anti-pentenediols with either olefin geometry can be synthesized from the same allenylboronate precursor 5. Furthermore, 1,5-pentenediols 4 and 6 can be easily converted to 1,3,5-triols with excellent diastereoselectivity in one step.
authors.affiliation: Department of Chemistry, Scripps Florida, Jupiter, Florida 33458, United States.
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.forename: William R
authors.initials: WR
authors.lastname: Roush
mesh_terms: D000466:Alkadienes / Q000737:chemistry*; D001880:Boranes / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D000439:Pentanols / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: C585547:2-methyl-1,5-anti-pentenediol; D000466:Alkadienes; D001880:Boranes; D000439:Pentanols