“…tetrahydrofurans, harsh conditions such as aqueous molecular bromine has been used to oxidatively ring-open THF to give 4-hydroxybutanal in only 20% yield ( Scheme 1 b). 4 A more recent paper by Leadbeater and co-workers pursued the transformation of 2-phenyltetrahydrofurans into 4-hydroxy-1-phenylbutane-1-ones by employing oxoammonium salts as oxidants ( Scheme 1 b). 3 The transformation is achieved by a hydride abstraction generating a stabilized carbocation.…”
A new method employing
iron(III) acetylacetonate along with visible
light is described to effect oxidative ring opening of cyclic ethers
and acetals with unparalleled efficiency. The method allows for a
photocatalytic radical chemistry approach to functionalize relatively
inert cyclic ethers into useful synthetic intermediates. The methodology
sheds further light on the use of underexplored iron complexes in
visible-light photochemical contexts and illustrates that simple Fe(III)
complexes can initiate redox processes from
4
LMCT excited
states.
“…tetrahydrofurans, harsh conditions such as aqueous molecular bromine has been used to oxidatively ring-open THF to give 4-hydroxybutanal in only 20% yield ( Scheme 1 b). 4 A more recent paper by Leadbeater and co-workers pursued the transformation of 2-phenyltetrahydrofurans into 4-hydroxy-1-phenylbutane-1-ones by employing oxoammonium salts as oxidants ( Scheme 1 b). 3 The transformation is achieved by a hydride abstraction generating a stabilized carbocation.…”
A new method employing
iron(III) acetylacetonate along with visible
light is described to effect oxidative ring opening of cyclic ethers
and acetals with unparalleled efficiency. The method allows for a
photocatalytic radical chemistry approach to functionalize relatively
inert cyclic ethers into useful synthetic intermediates. The methodology
sheds further light on the use of underexplored iron complexes in
visible-light photochemical contexts and illustrates that simple Fe(III)
complexes can initiate redox processes from
4
LMCT excited
states.
“…Indeed, the α-C atoms in both OEG and d- alkane chains are susceptible to the reaction with Br 2 , which generates carbonyl compounds, e.g., aldehydes from primary alkyl ethers. With excess of bromine further oxidation to carboxylic acids takes place . In our case, the reaction presumably stops at the stage of the aldehyde.…”
A self-assembled monolayer (SAM) on gold was formed with specifically perdeuterated hexaethylene glycol-terminated alkanethiol HS(CD(2))(12)(O-CH(2)-CH(2))(6)OCH(3) (D-OEG). The structure of the d-alkane and the oligoethylene glycol (OEG) parts of the molecule in a SAM was studied by means of polarization modulation infrared reflection absorption spectroscopy. The D-OEG monolayers are highly ordered and exist in a crystalline phase. The d-alkane chain adopts an all-trans conformation. Both, the d-alkane chain and long axis of the OEG part make an angle of 26.0 degrees +/- 1.5 degrees with respect to the surface normal, a value characteristic for the tilt of solid n-alkane thiols in the SAMs on Au. The positions of nu(as)(COC) and CH(2) wagging and rocking modes indicate a helical arrangement of the OEG chains. The D-OEG SAMs were exposed to 25 muM Br(2) in two ways: (i) by immersion into the Br(2) solution and (ii) in the galvanic cell Au|D-OEG SAM|25 muM Br(2) + 0.1 M Na(2)SO(4)|| 50 muM KBr + 0.1 M Na(2)SO(4)|Au. In the galvanic cell, the oxidant (Br(2)) is scavenged by a heterogeneous electron transfer reaction, slowing the reaction of D-OEG with Br(2). The slow progress of the reaction with Br(2) allowed us to draw conclusions about molecular rearrangements taking place during this reaction. The reaction with Br(2) starts on boundaries and/or defects present in the SAM. First, at the defect place, the alpha-C atom of the OEG chain reacts with Br(2) and the OEG part of the molecule is removed from the monolayer. In consequence an increase in disorder in the OEG part of the SAM is observed. The same mechanism of the reaction with Br(2) is applied for the d-dodecane alkanethiol part of the molecule. This reaction is slow, thus the order and the tilt of the hydrocarbon chain changes only a little during the reaction time.
“…After the ring expansion, a further reaction toward 3-bromopyrrolidin-2-ones 16 was observed, together with the formation of benzaldehyde. The mechanism of this reaction can be explained by attack of oxygen at bromine, followed by a dehydrobromination of the resulting oxonium ion 14 and a second-order nucleophilic substitution of “benzaldehyde” by bromide (Scheme ). − 6 …”
[reaction: see text] An efficient and straightforward route toward 3,4-cis-4-isopropenylazetidin-2-ones was developed from 4-(1-chloroalkyl)azetidin-2-ones. Starting from the latter beta-lactams, a new synthesis of pyrrolidin-2-ones was achieved. When 4-isopropenylazetidin-2-ones were treated with bromine in dichloromethane, diastereoselective electrophile-induced ring expansions toward 5-bromopyrrolidin-2-ones were performed. Further oxidation of 3-benzyloxypyrrolidin-2-ones with bromine toward 3-bromopyrrolidin-2-ones was also established. When 4-isopropenyl-beta-lactams were added to a mixture of NBS and TMSN(3), 5-azidopyrrolidin-2-ones were obtained in moderate to high yields.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
