Julia-Kocienski Olefination Reaction Research Articles

Latest Developments of the Julia-Kocienski Olefination Reaction: Mechanistic Considerations.

Since its discovery, the Julia-Kocienski olefination reaction has over past 30 years become one of the key C-C connective methods that is used in late-stage natural product synthesis. The reaction proceeds under mild reaction conditions, with a wide substrate scope and functional group tolerance range and with high (E) selectivity. In this focused review, we discuss the reaction from a mechanistic point of view and disclose key features that play an important role in reaction selectivity. Finally, the mechanistic aspects of the newly developed modification of the Julia-Kocienski reaction, which allows the formation of both (E) and (Z) olefins from the same reaction partners, are discussed.

Stereo flexible synthesis of the C8-C23 fragment of antarlides, androgen receptor antagonists.

A practical and efficient synthesis of the C8-C23 fragment of antarlides A-H, incorporating six stereocenters and a conjugated diene, is reported. A strategic combination of synthetic methods, including CBS reduction, Evans' aldol reaction, Keck-Maruoka allylation, and enzymatic resolution, enabled the selective introduction of these stereocenters. Furthermore, the pivotal coupling of key fragments is successfully executed through a Julia-Kocienski olefination reaction, connecting the C8-C14 and C15-C23 subunits.

Total Synthesis of (+)-Silybin A.

We report the first total synthesis of silybin A (1). Key synthetic steps include the construction of the 1,4-benzodioxane neolignan skeleton, a modified Julia-Kocienski olefination reaction between m-nitrophenyltetrazole sulfone (m-NPT sulfone) 10 and aldehyde 21, the formation of the flavanol lignan skeleton 28 via a quinomethide intermediate under acidic conditions, and stepwise oxidation of the benzylic position of flavanol 29.

Chemoenzymatic asymmetric total synthesis of naturally occurring resorcylic acid lactones hamigeromycins F and G.

Asymmetric total synthesis of two naturally occurring resorcylic acid lactones (RALs), hamigeromycins F and G, was achieved for the first time. The synthetic strategy involved a late-stage intramolecular macrolactonization achieved with a transesterification reaction. Stereocenters (C10' and C6') in both the molecules were accessed via an enzymatic kinetic resolution reaction. The penta-substituted aromatic core present in hamigeromycins F and G was accessed using vanillin as a precursor. The crucial E-olefinic unsaturated bond at C1'-C2' was constructed with a stereoselective Julia-Kocienski olefination reaction.

Two-Step Azidoalkenylation of Terminal Alkenes Using Iodomethyl Sulfones

The radical azidoalkylation of alkenes that was initially developed with α-iodoesters and α-iodoketones was extended to other activated iodomethyl derivatives. By using iodomethyl aryl sulfones, the preparation of γ-azidosulfones was easily achieved. Facile conversion of these azidosulfones to homoallylic azides using a Julia–Kocienski olefination reaction is reported, making the whole process equivalent to the azidoalkenylation of terminal alkenes.

Synthesis of an advanced intermediate enroute to thiomarinol antibiotics

A stereoselective synthesis of the C1-C14 fragment of thiomarinols is disclosed. The key steps include the stereoselective preparation of an allylic sulfide via a chloro sulfide by 1,2-asymmetric induction, ring-closing metathesis reaction, Kirmse-Doyle reaction for the preparation of a γ,δ-unsaturated ester, Nozaki-Hiyama-Kishi coupling and Julia-Kocienski olefination reaction. Substrate controlled asymmetric induction has been advantageously employed for the creation of stereogenic centers. Noyori transfer hydrogenation and asymmetric hydrogenation reactions have been utilized for the creation of carbinol stereocenters.

Carbonyl olefination of diaryl ketones with heteroaryl sulfoxides

Heteroaryl sulfones are capable of converting the carbonyl functionalities to alkenyl motifs, which is well-known as Julia–Kocienski olefination reaction. However, their sulfoxide analogues have failed in such an olefination reaction for over twenty years. In this Letter, we demonstrate that the heteroaryl sulfoxide-participated carbonyl olefination reaction can be realized under certain conditions. Furthermore, a novel defluorinative olefination of diaryl ketones has been achieved with 2-pyridyl sulfoxides.

Stereoselective Synthesis of the C13-C28 Subunit of (-)-Laulimalide Utilizing an α-Chlorosulfide Intermediate

A stereoselective route to the C13–C28 subunit of (–)-laulimalide is described. l -Tartaric acid is the source of the hydroxy groups at C19 and C20. An α-chlorosulfide is employed as the key intermediate for the creation of the C17–C18 bond and the C16–C17 double bond was introduced using the Mislow–Braverman rearrangement and Hutchin’s dexoxygenation with concomitant double bond transposition reaction. The C15 and C23 stereogenic centers were created using catalytic asymmetric reactions. The trisubstituted and trans -disubstituted alkenes were created stereoselectively by taking advantage of ring-closing metathesis and the Julia–Kocienski olefination reaction, respectively.

Ready Synthetic Access to Enantiopure Allylic α(F)-Branched Fluoroalkenes

Convenient access to homochiral fluoroalkenes is described via a Julia-Kocienski olefination reaction. The required homochiral fluorosulfone is synthesized by a Mitsunobu reaction from readily available enantiopure secondary alcohols.

Julia–Kocienski Reaction-Based 1,3-Diene Synthesis: Aldehyde-Dependent (E,E/E,Z)-Selectivity

A new modification of Julia-Kocienski olefination reaction based on the use of cation-specific chelating agents that yields 1,3-dienes with predictable (E/Z)-selectivity on newly created double bond was developed. The influence of the aldehyde structure on reaction (E/Z) selectivity is discussed and rationalized.

A Fully Conjugated TTF–π–TCAQ System: Synthesis, Structure, and Electronic Properties

The synthesis of the first fully conjugated tetrathiafulvalene-tetracyano-p-quinodimethane ((TTF)-TCNQ)-type system has been carried out by means of a Julia-Kocienski olefination reaction. In particular, a tetracyanoanthraquinodimethane (TCAQ) formyl derivative and two new sulfonylmethyl-exTTFs (exTTF = 2-[9-(1,3-dithiol-2-ylidene)anthracen-10(9H)-ylidene]-1,3-dithiole)--prepared as new building blocks--were linked. A variety of experimental conditions reveal that the use of sodium hexamethyldisilazane (NaHMDS) as base in THF afforded the E olefins with excellent stereoselectivity. Theoretical calculations at the B3LYP/6-31G** level point to highly distorted exTTF and TCAQ that form an almost planar stilbene unit between them. Although calculations predicted appreciable electronic communication between the donor and the acceptor, cyclic voltammetric studies did not substantiate this effect. It was only in photophysical assays that the electronic communication emerged in the form of a charge-transfer (CT) absorption and emission. Once photoexcited (i.e., the locally excited state or excited charge-transfer state), an ultrafast, subpicosecond charge separation leads to a radical ion pair state in which the spectroscopic features of the radical cation of exTTF as well as the radical anion of TCAQ are discernable. The radical ion pair is metastable and undergoes a fast ((1.0±0.2) ps) charge recombination to reconstitute the electronic ground state. Such ultrafast charge separation and recombination processes come as a consequence of the very short vinyl linkage between the two electroactive units.

Practical and efficient approach to the synthesis of guineensine

A total synthesis of guineensine, a secondary metabolite of the Piperaceae family, has been executed in 12 steps with an overall yield of 27%. Key steps in the synthesis featured novel application of a Julia–Kocienski olefination reaction which effectively constructed alkenamide skeleton. This contributes a unique approach to the synthesis of the piperamide alkaloids.

1- tert-Butyl-1 H-tetrazol-5-yl fluoromethyl sulfone (TBTSO 2CH 2F): a versatile fluoromethylidene synthon and its use in the synthesis of monofluorinated alkenes via Julia–Kocienski olefination

1- tert-Butyl-1 H-tetrazol-5-yl fluoromethyl sulfone (TBTSO 2CH 2F) has been developed as a new and efficient fluoromethylidene synthon for the synthesis of both terminal and internal monofluoroalkenes via Julia–Kocienski olefination reaction. The base-mediated reaction between TBTSO 2CH 2F and carbonyl compounds (aldehydes and ketones) provided terminal monofluoroalkenes in good yields with moderate E/ Z selectivity. The dominance of E- or Z-fluoroalkenes could be controlled by selection of proper reaction solvent and temperature. TBTSO 2CH 2F reagent was also found to be readily α-alkylated, acylated, and phenylsulfonylated to give corresponding α-functionalized fluorosulfones, which could be used in the synthesis of alkyl-, acyl-, and phenylsulfonyl-substituted internal monofluoroalkenes via Julia–Kocienski olefination reactions.

Synthesis of Isopeptide Epoxide Peptidomimetics

Two epoxide-containing peptidomimetics of the isopeptide, glutamyl-gamma-glutamate, have been synthesized via a route that should be generally applicable to the synthesis of isopeptide analogues in which an oxirane replaces the scissile peptide bond. Enzymes that catalyze the hydrolysis of peptides and isopeptides are often susceptible to inactivation by electrophilic substrate analogues. In this research, an epoxide was installed as an electrophilic replacement of the scissile isopeptide bond. The C-terminal glutamyl mimic was accessed by the stereospecific synthesis of suitably substituted cyclopentenes, 8 and 10, as surrogates for either the L- or D-enantiomer. The enantiomeric cyclopentenes were further elaborated to incorporate an appended sulfone that was reacted with a suitably protected glutamyl-gamma-semialdehyde in a Julia-Kocienski olefination reaction. This olefination afforded predominantly the desired E-olefin isosteres of L-glutamyl-gamma-D-glutamate and L-glutamyl-gamma-L-glutamate, following which peracid-mediated epoxidation and deprotection provided the epoxide-containing peptidomimetics, 4 and 5.

3,5‐Bis(trifluoromethyl)phenyl Sulfones in the Modified Julia Olefination: Application to the Synthesis of Resveratrol.

AbstractFor Abstract see ChemInform Abstract in Full Text.

3,5-Bis(trifluoromethyl)phenyl sulfones in the modified Julia olefination: application to the synthesis of resveratrol

The reaction between carbanions derived from alkyl 3,5-bis(trifluoromethyl)phenyl sulfones and aldehydes, affords with good yields and stereoselectivities the corresponding 1,2-disubstituted alkenes through the Julia–Kocienski olefination reaction. This one-pot protocol can be performed using KOH at room temperature or the phosphazene base P4- t-Bu at −78 °C, and has been successfully used in a high yielding and stereoselective synthesis of various stilbenes such as resveratrol.