Synthesis of the core structure of cruentaren A

The core structure of the macrolactone cruentaren A (1) was prepared via a ring-closing alkyne metathesis reaction. The corresponding ester 33 was constructed from the benzoic acid derivative 14 and the diol 30. As a key step in the synthesis of acid 14, an aldol reaction resulted in the required anti-OH/Me pattern. The anti-configuration in the stereotetrad of diol 30 was established by a Marshall reaction. [reaction: see text].     

Practical and efficient multigram preparation of a camphor-derived diol for the enantioselective Lewis acid catalyzed allylboration of aldehydes

[reaction: see text] Chiral diols are important molecules with widespread use as chiral auxiliaries and ligands in enantioselective synthesis. Therefore, efficient and practical syntheses of highly dissymmetrical nonracemic diols are still a meaningful pursuit. Two new routes to access camphor-derived chiral diol 1 have been developed. One route employs camphorquinone (3) as the starting material, affording in only two steps the desired diol in 55% overall yield. The second route, from camphor (2), leads to the desired diol in an efficient four-step synthesis, with an overall yield of 55%.     

A general strategy for the synthesis of vincamajine-related indole alkaloids: stereocontrolled total synthesis of (+)-dehydrovoachalotine, (-)-vincamajinine, and (-)-11-methoxy-17-epivincamajine as well as the related quebrachidine diol, vincamajine diol, and vincarinol

[structures: see text] The highly convergent stereocontrolled total synthesis of (-)-vincamajinine (7), (-)-11-methoxy-17-epivincamajine (9), and the oxygen-bridged (+)-dehydrovoachalotine (22) are described. Key steps in the synthesis of 7 and 9 involved the stereospecific enolate-driven palladium-catalyzed cross-coupling reaction, a Tollens reaction, an acid-assisted intramolecular cyclization to form the C(7)-C(17) quaternary center, and two stereospecific reductions. The efficiency of this strategy is illustrated by the completion of the synthesis of 7 and 9 in 16 [from d-(+)-tryptophan methyl ester 17] and 17 (from the Sch?llkopf chiral auxiliary 27) reaction vessels, respectively. This constitutes the first total synthesis of these indole alkaloids and provides the first regiospecific route to 11-methoxy-substituted ajmaline/vincamajine-related alkaloids. The synthesis of 22 required a novel DDQ-mediated cyclization to furnish the C(6)-O(17) bond, executed in stereospecific fashion. Completion of these syntheses illustrates a concise and versatile strategy for the synthesis of vincamajine-related alkaloids, which has also been employed to prepare the related compounds quebrachidine diol (53), vincamajine diol (56), and vincarinol (59).     

A New and Concise Synthesis of 3-Hydroxybenzo[c]phenanthrene and 12-Hydroxybenzo[g]chrysene, Useful Intermediates for the Synthesis of Fjord-Region Diol Epoxides of Benzo[c]phenanthrene and Benzo[g]chrysene

A new strategy which involves a palladium-catalyzed cross-coupling reaction has been developed for the rapid synthesis of 3-hydroxybenzo[c]phenanthrene (5) and 12-hydroxybenzo[g]chrysene (6). These phenolic compounds are the key intermediates for the synthesis of highly carcinogenic fjord-region diol epoxide metabolites 3 and 4 of benzo[c]phenanthrene (1) and benzo[g]chrysene (2). The cross-coupling reaction of 2-bromo-5-methoxybenzaldehyde (9) with naphthalene-1-boronic acid (7) and phenanthrene-9-boronic acid (8) produced 2-(1-naphthyl)-5-methoxybenzaldehyde (10) and 2-(9-phenanthryl)-5-methoxybenzaldehyde (11), respectively, in quantitative yields. After reaction of these aldehydes with trimethylsulfonium iodide under phase-transfer conditions or with the Wittig reagent obtained from (methoxymethyl)triphenylphosphonium bromide and phenyllithium to generate an oxiranyl or methoxyethene side chain, the acid-catalyzed cyclization with methanesulfonic acid (or boron trifluoride) produced 3-methoxybenzo[c]phenanthrene (16) and 12-methoxybenzo[g]chrysene (17) in 61-64% yields. Finally, demethylation of these methoxy derivatives 16 and 17 with boron tribromide resulted in the formation of the hydroxy analogues 5 and 6, respectively. The availability of this short and high-yielding regiospecific method for the synthesis of phenols 5 and 6 should allow the preparative-scale synthesis of the fjord-region diol epoxides 3 and 4. These diol epoxides are required as starting compounds for the synthesis of site-specifically modified oligonucleotides which are critically needed to elucidate the mechanism of carcinogenesis at the molecular level.     

Activated carbon supported Co1.5PW12O40 as efficient catalyst for the production of 1, 2 cyclohexane diol by oxidation of cyclohexene with H2O2 in the presence of CO2

ABSTRACT

Vicinal diols are important building blocks for chemicals and pharmaceuticals. Currently, they are produced from olefins using solvents and harmful oxidants unfavorable from an environmental and economic point of view. This work lies on the synthesis of 1,2 cyclohexane diol from cyclohexene by a green route. To achieve it, a series of Cobalt Keggin heteropolyanion salt (Co_1.5PW₁₂O₄₀) loaded on activated carbon with different contents was prepared, characterized and tested for the synthesis of diol. The effect of various parameters such as reaction temperature, reaction time and CO₂ pressure on the reaction was studied. The effect of reaction temperature in the range 60-80 °C showed that high temperatures favor diol formation while low temperatures favor cyclohexanone and a segmented concave Arrhenius graph was observed. The results of this work showed that oxidation by H₂O₂ in the presence of CO₂ is an efficient oxidant system for the production of 1.2 cyclohexane diol over carbon activated carbon supported Co_1.5PW₁₂O₄₀. Thanks to CO₂ as a soft oxidizing agent, a conversion of 96.9% and a selectivity in 1, 2 cyclohexane diol of 64.2% was obtained. This simple, safe and environmentally method could be an alternative green route for vicinal diols production from alkenes.     

Asymmetric synthesis of naproxen via a pinacol-type reaction

An asymmetric pinacol-type rearrangement was used in the synthesis of (S)-naproxen. The pinacol-type reaction of a vicinal diol provided an -aryl ketone which was oxidized with sodium hypochlorite in the presence of methanol to the methyl ester of naproxen.     

Asymmetric synthesis of (−)-tetrahydrolipstatin

Attempts toward the asymmetric synthesis of (−)-tetrahydrolipstatin are described. A palladium catalyzed Wacker-type reaction to convert an alkene to a ketone, highly diastereoselective reduction of a β-hydroxy ketone, selective oxidation of a diol, and modular synthesis are the key features of the successful approach.     

Synthesis of cyclic oligo(ethylene adipate)s and their melt polymerization to poly(ethylene adipate)

We present here the first synthesis of cyclic oligo(ethylene adipate)s(COEAs) via pseudo-high dilution condensation reaction of adipoyl chloride with ethylene glycol, and the synthesis of corresponding poly(ethylene adipate)(PEA) via the melt polymerization of COEAs. The structure of COEAs was characterized and proved by 1H-NMR and MALDI-TOF mass measurements. The effects of organic base, reaction temperature and the ratio of adipoyl chloride to ethylene glycol on the yield of COEAs were studied, and the optimum reaction condition was revealed. PEA, a diacid and diol based semi-crystalline green aliphatic polyester, was synthesized by the melt polymerization of COEAs using Ti(n-C4H9O)4 as catalyst and 1,10-decanediol as initiator at 200 °C, which follows the polycondensation-coupling ringopening polymerization method. Our strategy should be applicable to the synthesis of versatile aliphatic polyesters based on diacid and diol monomers, which have potential applications as biocompatible and biodegradable materials.     

Synthesis and characterization of radiopaque poly(ether urethane) with iodine‐Containing diol as chain extender

Novel radiopaque iodinated poly(ether urethane) (IPEU) was prepared by using iodine‐containing diol as chain extender in a normal two‐step condensation polymerization process. This new iodine‐containing diol was synthesized by iodination of terephthalic acid and then reaction with 3‐aminopropanol. The chemical structure of the diol chain extender and IPEU was characterized, and the basic properties of IPEU were measured and compared with PEU. X‐ray images showed that 15 wt % iodine‐containing IPEUs were highly radiopaque, and radiopacity did not decrease after 6‐week oxidative degradation treatment. Experimental results showed that IPEUs possessed good thermal stability, favorable mechanical properties, and noncytotoxicity. These results reveal that it is an effective route for the synthesis of biological polyurethane with radiopacity by using iodine‐containing diol as chain extender. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Transition-state effects in acid-catalyzed aryl epoxide hydrolyses

The hydronium ion-catalyzed hydrolyses of 5-methoxyindene 1,2-oxide and of 6-methoxy-1,2,3,4-tetrohydronaphthalene-1,2-epoxide were each found to yield 75-80% of cis diol and only 20-25% of trans diol as hydrolysis products. The relative stabilities of the cis and trans diols in each system were determined by treating either cis or trans diols with perchloric acid in water solutions and following the approach to an equilibrium cis/trans mixture as a function of time. These studies establish that the trans diol in each system is more stable than the corresponding cis diol. Thus, acid-catalyzed hydrolysis of each epoxide, which proceeds via a carbocation intermediate, yields the less stable cis diol as the major product. Transition-state effects, presumably of a hydrogen-bonding nature, selectively stabilize the transition state for attack of water on the intermediate 2-hydroxy-1-indanyl carbocation leading to the less stable cis diol in this system. Transition-state effects must also be responsible for formation of the less stable cis diol as the major product in the acid-catalyzed hydrolysis of 5-methoxy-1,2,3,4-tetrahydronaphthalene 1,2-epoxide. However, in this system steric effects at the transition state may be more important than hydrogen bonding in determining the cis/trans diol product ratio. The synthesis of 5-methoxyindene 1,2-oxide and a study of its rate of reaction as a function of pH in water and dioxane-water solutions are reported. Both an acid-catalyzed reaction leading to only diol products and a pH-independent reaction yielding 71% of 5-methoxy-2-indanone and 29% of diols are observed; the half-life of its pH-independent reaction in water is only 2.4 s.     

Asymmetric cleavage of chiral acetals by R2CuLi,BF3 reagents

The title reagents cleave diastereoselectively the acetals derived from various aldehydes and chiral 2–3 butane diol (or higher homologs). This reaction affords an asymetric synthesis of secondary alcohols from an aldehyde and a trivial organolithium reagent.     

Synthesis of amphidinolide E C10-C26 fragment

The key C10-C26 fragment in a total synthesis of (-)-amphidinolide E has been prepared from an oxolane-containing C10-C17 segment (9, derived from L-glutamic acid) via a Julia-Kocienski reaction with aldehyde 3, followed by a Sharpless AD to obtain the desired diol. The C22-C26 fragment was installed by means of an efficient Suzuki-Molander coupling, with an organotrifluoroborate reagent (4, arising from a cross-metathesis reaction between a vinylboronate and 2-methyl-1,4-pentadiene).     

An effective and highly stereoselective Julia olefination of cyclopropyl carbinol mediated by CeCl3.7H2O/NaI

[reaction: see text] An efficient and highly stereoselective synthesis of functionalized trisubstituted E-olefins from cyclopropyl carbinol derivatives via a Julia-type olefination mediated by an intriguing Lewis acidic system consisting of CeCl(3).7H(2)O and NaI in refluxing acetonitrile is reported. This facile olefination allows for the iterative incorporation of methylcyclopropyl ketone as a C(5) prenylation synthon in the synthesis of acyclic terpenoids, as demonstrated in the facile synthesis of plaunotol 6E-isomer 12, a biologically significant diterpene diol, and naturally occurring diterpene 17.     

Formal synthesis of (−)-morphine from d-glucal based on the cascade Claisen rearrangement

The formal synthesis of (−)-morphine is described. The C-ring in morphine was prepared in an optically pure form from d-glucal using Ferrier’s carbocyclization reaction, and the vicinal tertiary and quaternary stereocenters in the C-ring were stereoselectively generated in a one-step reaction based on the cascade sequential Claisen rearrangement of an allylic vicinal diol derivative. After the one-step formation of the dibenzofuran structure, the intramolecular Friedel-Crafts type reaction effectively constructed the ABCE-phenanthrofuran skeleton. Introduction of a tosylamide function, followed by reductive cyclization furnished (−)-dihydroisocodeine, the known synthetic intermediate for (−)-morphine.     

Synthesis and physical properties of poly(urethane)s using vicinal diols derived from acrylate and styrene monomers

We describe the utilization of four kinds of diol derivatives, representing structural similarity to the well‐known and commercially available vinyl monomers such as acrylate, acrylamide, styrene, and N‐substituted maleimide. The vinyl monomers are readily converted by dihydroxylation reaction to afford the vicinal diol. The synthesis of poly(urethane)s was performed by the reaction of the vicinal diol with two model diisocyanates, including methylene diphenyl isocyanate (MDI) and hexamethylene diisocyanate (HDI) in the presence of dibutyltin dilaurate to form a series of poly(urethane)s, and the effect of vicinal diol containing a side chain inherited from vinyl monomers on their thermal and mechanical properties was investigated using thermogravimetric analysis, differential scanning calorimetry, and tensile test. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 799–805     

[60]Fullerene diol issued from pentaerythritol derivatives

A new [60]fullerene diol is synthesized in good yield, in two steps starting from reaction of C₆₀²⁻ anion with the benzylideneacetal derived from 2,2-bis(iodomethyl)-1,3-propanediol. The corresponding [60]fullerene bis-mesylate is also formed in a similar way starting from bis-iodo bis-mesylate compound in the same series. The scope of this fullerene diol in synthesis is exemplified by its easy esterification with 4-formyl benzoyl chloride.     

Synthesis of aza-, oxa-, and thiabicyclo[3.1.0]hexane heterocycles from a common synthetic intermediate

[reaction: see text] An efficient and stereospecific approach to the synthesis of structurally constrained aza-, oxa-, and thiabicyclo[3.1.0]hexane heterocycles has been achieved through application of the intramolecular cyclopropanation reaction of diazoacetates. The various constrained heterocycles (X = N, O, or S) are conveniently prepared from a common diol intermediate accessible from readily available cinnamyl alcohols. Application of the methodology to the synthesis of conformationally constrained oxazolidinone antibacterials is also discussed.     

Formal total synthesis of (-)-apicularen A via transannular conjugate addition

The formal total synthesis of the myxobacteria metabolite (-)-apicularen A (1) is described. The key step involved a novel acid-mediated transannular conjugate addition of the C13 hydroxyl into the alpha,beta-unsaturated ketone in either of the macrolactones 5a or 5b to provide the same trans-pyranone 4. Conversion of 4 into the known apicularen intermediate diol 3 completed the formal synthesis. [reaction: see text]     

Divergent asymmetric synthesis of 3,5-disubstituted piperidines

A divergent synthesis of various 3,5-dioxygenated piperidines with interesting pharmacological properties is described. A mixture of the achiral cis- and racemic trans-3,5-piperidine diol could be efficiently obtained from N-benzylglycinate in five steps by the use of chemoenzymatic methods. In the subsequent enzyme- and Ru-catalyzed reaction, the rac/meso diol mixture was efficiently transformed to the cis-(3R,5S)-diacetate with excellent diastereoselectivity and in high yield. Further transformations of the cis-diacetate selectively delivered the cis-piperidine diol and the cis-(3R,5S)-hydroxy acetate. Alternatively, the DYKAT could be stopped at the monoacetate stage to give the trans-(3R,5R)-hydroxy acetate.     

Total synthesis of (+)-boronolide, (+)-deacetylboronolide,and (+)-dideacetylboronolide

Total synthesis of (+)-boronolide, (+)-deacetylboronolide, and (+)-dideacetylboronolide has been achieved from a single intermediate 26, which was synthesized in 11 steps from a d-mannitol-derived intermediate 8 in an overall yield of 10%. The key steps in the synthesis are inversion of a chiral center by taking an advantage of the inherent mechanism involved in the ring closing to an epoxide via intramolecular S(N)2 reaction and lactonization of a diol using Fetizons reagent. The strategy is amenable to preparation of analogues of (+)-boronolide in sufficient amount for further screening of biological activity.