An Overview of Debenzylation Methods to Obtain 1-Deoxynojirimycin (DNJ)

A classic reductive amidation/amination (C-N bond formation) approach for DNJ synthesis has been widely practiced due to the availability of low-cost reagents. The key steps for this synthetic route are Swern oxidation, reductive amidation/amination, and debenzylation. A lot of attention has been given to the optimization of these key intermediates apart from debenzylation. This review aims to describe the deprotection advances employing efficient, systematic, and practical protocols for sample preparation and separation by using Pd(OH)2/C, Li, BCl3 and Pd/C as catalysts. The impact of varying reaction parameters such as solvents, acids and temperature for deprotection was emphasized for optimal DNJ synthesis.

Synthesis of Optically Active Maresin 2 and Maresin 2n-3 DPA

Maresins are among the most potent antiinflammatory lipid metabolites. We report stereoselective syntheses of maresin 2 and maresin 2n-3 DPA. The anti-diol was constructed through epoxide ring opening of an optically active β,γ-epoxy aldehyde, synthesized in situ by Swern oxidation of the corresponding alcohol. Finally, the target compounds were synthesized through a Sonogashira coupling of a C9–C22 iodide and methyl (Z)-oct-4-en-7-ynoate or methyl oct-7-ynoate, respectively.

Optimization of continuous-flow diphenyldiazomethane synthesis: an integrated undergraduate chemistry experiment

We present a challenging flow-chemistry experiment concerning the synthesis of diphenyldiazomethane using the Omura-Sharma-Swern oxidation, that we have developed and used in our second-year undergraduate lab classes over the past seven years. The experiment integrates a number of different aspects and concepts of chemistry that are traditionally taught as separate subjects in undergraduate chemical education: organic synthesis, quantitative chemical analysis, design of experiments, optimization, statistical modelling, computer programming and continuous-flow processes.

Synthesis and structure of 2,4,6-tricyclobutyl-1,3,5-trioxane

The synthesis and structure of 2,4,6,-tricyclobutyl-1,3,5-trioxane, C15H24O3 1, is described. It was formed in 39% yield during the work-up of the Swern oxidation of cyclobutylmethanol and may serve as a stable precursor of the cyclobutane carbaldehyde. The molecule of 1 occupies a special position (3.m) located at the center of its 1,3,5-trioxane ring. The latter is in a chair conformation, with the symmetry-independent O and C atoms deviating by 0.651 (4) Å from the least-squares plane of the other atoms of the trioxane ring. All three cyclobutane substituents, which have a butterfly conformation with an angle between the two planes of 25.7 (3)°, are in the cis conformation relative to the 1,3,5-trioxane ring. Intermolecular C—H...O interactions between the 1,3,5-trioxane rings consolidate the crystal structure, forming stacks along the c-axis direction. The crystal studied was refined a as a racemic twin.

Cyclopropenium-Activated DMSO for Swern-Type Oxidation

Swern oxidation is widely used to convert alcohols into their corresponding carbonyl compounds. However, the conventional method with use of the volatile oxalyl chloride as an activator requires the reaction to be conducted below −60 °C. We discovered that 3,3-dichloro-1,2-diphenylcyclopropene (DDC) can be used as a new activator for Swern-type oxidations of alcohols, which can be conducted at −20 °C. This new protocol features mild and fast reactions with easy operation. Furthermore, the activator DDC is easy to handle, and diphenylcyclopropenone can be recovered quantitively. This new type of Swern oxidation shows a broad scope of substrates including benzylic, allylic, aliphatic, and biobased alcohols, and gives high yields of up to 93%.

Synthesis of Substrates for Aldolase-Catalysed Reactions: A Comparison of Methods for the Synthesis of Substituted Phenylacetaldehydes

Methods for the synthesis of phenylacetaldehydes (oxidation, one-carbon chain extension) were compared by using the synthesis of 4-methoxyphenylacetaldehyde as a model example. Oxidations of 4-methoxyphenylethanol with activated DMSO (Swern oxidation) or manganese dioxide gave unsatisfactory results; whereas oxidation with 2-iodoxybenzoic acid (IBX) produced 4-methoxyphenylacetaldehyde in reasonable (75%) yield. However, Wittig-type one-carbon chain extension with methoxymethylene-triphenylphosphine followed by hydro­lysis gave an excellent (81% overall) yield of 4-methoxyphenylacetaldehyde from 4-methoxybenzaldehyde (a cheap starting material). This approach was subsequently used to synthesise a set of 10 substituted phenylacetaldehydes in good to excellent yields.