169. The mechanism of epoxide reactions. Part V. The reaction of 1,2-epoxypropane with chloride ion in water under neutral and acidic conditions

Asymmetric Synthesis of the Tropane Alkaloid (+)-Pseudococaine via Ring-Closing Iodoamination

“…Recrystallization of this mixture from CH 2 Cl 2 /Et 2 O enabled the relative configuration within 17 to be unambiguously assigned via single crystal X-ray diffraction analysis (Figure ), and the determination of a Flack x parameter of −0.04(3) for the crystal structure of 17 allowed the absolute (1 R ,2 S ,3 S ,4 R ,5 S )-configuration within 17 (and therefore the absolute configurations within 10 and 14 ) to be unambiguously assigned. This stereochemical outcome is entirely consistent with our previous observations concerning this class of ring-closing iodoamination reaction and a mechanism in which reversible formation of iodonium ion 15 is followed by cyclization of the amino group onto the C(4) carbon atom [i.e., distal to the C(2)-hydroxyl group] , to give ammonium ion 16 . Subsequent loss of the α-methyl- p -methoxybenzyl cation then gives 8-azabicyclo[3.2.1]octane 17 , and the α-methyl- p -methoxybenzyl cation is trapped by EtOH giving 18 ; , presumably the formation of 19 occurs via a similar N -oxidation pathway.…”

An Oxidation and Ring Contraction Approach to the Synthesis of (±)-1-Deoxynojirimycin and (±)-1-Deoxyaltronojirimycin

“…The relative configuration within 13 was unambiguously established by single-crystal X-ray analysis (Figure ), and the relative configuration within 12 was established by chemical correlation: resubjection of 12 to the oxidation reaction conditions promoted conversion to 13 as a single diastereoisomer in 62% isolated yield. These results are consistent with a mechanism involving epoxidation of the double bond followed by highly regioselective ring opening of the intermediate epoxide 11 by BnOH at C(4), which is both remote from the destabilizing influence of the electron-withdrawing, protonated nitrogen atom in the late transition state and an activated allylic site . In the presence of excess m -CPBA, the intermediate monobenzyl protected diol 12 is further oxidized in a diastereoselective manner to give the monobenzyl protected diol epoxide 13 (Scheme ).…”

.alpha.,.alpha.'-Dibromocycloalkanols and 3-bromocycloalkene oxides

“…Epoxidation of 3-bromocyclooctene (10) gave trans-3-bromocyclooctene oxide (11), which was converted to irons,írans-2,8-dibromocyclooctanol (12) by treatment with hydrobromic acid. Oxidation of 12 using the Jones procedure afforded cis -2,8-dibromocyclooctanone (13).…”