2-Halo-2-cyclohexenols from 6,6-Dihalobicyclo-[3.1.0]hexanes and Dimethyl Sulfoxide. Studies towards a Non-basic Hydroxide Equivalent.
摘要:
A practical, high yielding, cheap and mild method for the synthesis of 2-halo-2-cycloalkenols, especially 2-bromo-2-cyclohexenol, is reported. Direct conversion from a variety of thermally labile n,n-dihalobicyclo[n-3.1.0]alkanes to 2-halo-2-cycloalkenols can be achieved without using silver salts by simple heating in DMSO. The intermediate 1,n-dihalocycloalkenes immediately undergo indirect allylic substitution with DMSO to yield the corresponding halocycloalkenols. A possible mechanism for the substitution step comprises nucleophilic attack by DMSO followed by a Pummerer rearrangement and hydrolytic decomposition. Kinetic and mechanistic experiments to verify the course of the reaction are presented.
A Mild Method for the Generation and Interception of 1,2-Cycloheptadienes with 1,3-Dipoles
作者:Yaseen A. Almehmadi、F. G. West
DOI:10.1021/acs.orglett.0c02172
日期:2020.8.7
Seven-membered cyclic allenes are mostly known for their propensity to undergo rapid dimerization, and relatively little has been reported regarding their cycloaddition reactivity with 1,3-dienes or 1,3-dipoles. This work describes the trapping of 1-acetoxy-1,2-cycloheptadiene and its unsubstituted counterpart, generated via desilylative elimination, with a range of 1,3-dipolar trapping partners, affording
α-Methylene-β-lactams 3 were synthesized from the various 2-bromoallylamine derivatives 2 using a catalytic amount of Pd(OAc)2 or PD(acac)2 and PPh3, under 1–4 atom pressure of CO in good yields. Similarly, α-alkylidene-β-lactams 20 were synthesized from 3-alkyl-2-bromoallylamines 19, which were easily prepared from the olefins 14, in the same manner.