A monolithic and flexible polyimide film microreactor is introduced for organic reactions and syntheses. Unlike glass microreactors, it is easy to fabricate, yet it is inert to solvents and acids under harsh conditions, unlike other polymer microreactors.
The free-radical-mediated bromoallylation of acetylenes proceeded efficiently in the presence of V-65 (2,2-azobis(2,4-dimethylvaleronitrile)) as the radical initiator. The regioselective reaction, which yields 1-bromo-2-substituted 1,4-dienes, is complementary to the Pd-catalyzed bromoallylation reaction previously reported by Kaneda. The products of the free-radical-mediated bromoallylation of acetylenes could be converted into a variety of substituted dienes by subsequent Pd-catalyzed reactions.
Diastereoselective [2 + 2] photocycloaddition of chiral cyclohexenone 1 with cyclopentene was conducted using a continuous microflow reactor. This reaction led to photoadducts 2 and 3 in a shorter reaction time and with a higher diastereoselectiviy than the corresponding reaction in a batch reactor. The effect of temperatures on the selectivities of both reaction systems is also discussed.
A high-boiling, fluorous-organic hybrid ether, F-626, was tested for use in thermal retro-aldol reactions and found to be an excellent reaction medium in view of the ease of separation from the product by fluorous/organic biphasic treatment. The recovered F-626 can be readily reused for subsequent runs.
Competitive kinetic experiments utilising free radical carbonylation chemistry provide a first estimate for the rate constant for 6-endo cyclization of the 6-aza-7-ethyl-5-hexenoyl radical of (4.8 ± 2.4) × 106 s−1 at 90° C in benzene, in good agreement with ONIOM-G3(MP2)-CC+COSMO-RS calculations (6.8 × 106 s−1).
A triphasic phase-vanishing (PV) system comprised of an alkane, perfluorohexanes, and bromine was successfully combined by photoirradiation to efficiently generate hydrogen bromide, which underwent radical addition with 1-alkenes in the hydrocarbon layer to afford terminal bromides in high yields.
A novel [5+1] type carbonylative cycloaddition reaction has been developed using a Rh complex as catalyst. This reaction can convert readily available 3-acyloxy-1,4-enynes and CO to a wide range of functionalized resorcinols in good yields. A mechanism involving Rh-catalyzed cyclocarbonylation of 3-acyloxy-1,4-enynes accompanied by a 1,2-acyloxy shift is proposed for the present [5+1] type cycloaddition reaction.
Under photoirradiation conditions using xenon light, in the presence of a catalytic amount of PdCl2(PPh3)2 with triethylamine as a base, a three-component coupling reaction of iodoalkanes, carbon monoxide, and terminal alkynes proceeded to give alkyl alkynyl ketones in good yields.
The potential of hydrazine group as the new radical leaving group was studied. Radical cyclization of (E)-1,1-dialkyl-2-(1-alkyloct-2-en-7-ynyl)hydrazines with n-Bu3SnH/AIBN, followed by protodestannylation, gave 1-alkenyl-2-methylenecyclopentanes, which arose by 5-exo cyclization and subsequent β-elimination of hydrazyl radical.
Tin-free radical/ionic hydroxymethylation of secondary and tertiary alkyl iodides proceeded efficiently in the presence of tetrabutylammonium borohydride as the hydrogen source under atmospheric pressure of CO in conjunction with photoirradiation using black light. Two possible mechanisms were proposed, both of which involve hybrid radical/ionic processes.
The cross-coupling reaction of α,β-unsaturated aldehydes with primary alcohols to give 2-hydroxymethyl ketones was achieved using RuHCl(CO)(PPh3)3 as a catalyst. This atom-economical reaction is likely to proceed via the hydroruthenation of α,β-unsaturated aldehydes followed by an aldol reaction of the resultant enolates with aldehydes to give α-formylated ketones, which undergo transfer hydrogenation with primary alcohols leading to α-hydroxymethyl ketones. The reduction step can generate aldehydes, participating in the next catalytic cycle.