Asymmetric Total Synthesis of Hispidanin A

Asymmetric total synthesis of the dimeric diterpenoid hispidanin A was accomplished by non-catalytic Diels–Alder cycloaddition at room temperature. The synthesis relies on iron-catalyzed coupling to construct a Z-configured trisubstituted alkene, an iron-catalyzed radical cascade to generate a labdane-type diene, and both Yamamoto cationic polyene cyclization and palladium-catalyzed Stille coupling to generate a totarane-type dienophile.     

A general route to the Streptomyces-derived inthomycin family: the first synthesis of (+)-inthomycin B

A concise, convergent and stereocontrolled synthesis of (+)-inthomycin B, based on the Stille coupling of a stannyl-diene with an oxazole vinyl iodide unit, is described. The asymmetric centre was introduced using the Kiyooka ketene acetal/amino acid-derived oxazaborolidinone procedure.     

Synthesis of a functionalized dialkynylferrocene for molecular electronics

The first preparation of a 1,1′-dialkynylferrocene containing two thioacetyl units as alligator clips for the application as molecular wires by a Stille coupling is described. A building block principle for the synthesis of longer and more complicated molecular wires containing more than one ferrocene unit is presented. To cite this article: M. Vollmann, H. Butenschön, C. R. Chimie 8 (2005).     

2,2′‐Bi[benzo[b]thiophene]: an unexpected isolation of the benzo[b]thiophene dimer

The crystal structure of 2,2′‐bi[benzo[b]thiophene], C₁₆H₁₀S₂, at 173 K has triclinic (P) symmetry. It is of interest with respect to its apparent mode of synthesis, as it is a by‐product of a Stille cross‐coupling reaction in which it was not explictly detected by spectroscopic methods. It was upon crystal structure analysis of a specimen isolated from the mother liquor that this reaction was determined to give rise to the title compound, which is a dimer arising from the starting material. Two independent half‐molecules of this dimer comprise the asymmetric unit, and the full molecules are generated via inversion centers. Both molecules in the unit cell exhibit ring disorder, and they are essentially identical because of their rigidity and planarity.     

A comprehensive survey of stille-type Csp-Csp single bond forming processes in the synthesis of retinoic acid and analogs

The synthesis of the retinoid skeleton has been exhaustively explored using the Stille coupling for the formation of the side-chain single bonds. On employing the experimental catalytic conditions developed by Farina [Pd₂(dba)₃, AsPh₃, NMP] we have modified the electronic and steric requirement of the coupling parters, alkenyl stannanes and electrophiles (alkenyl iodides and triflates). The comprehensive survey afforded appropriately matched components for every bond formation considered. Moreover, from the comparison of the reactivities of different coupling partners with different degrees of steric hindrance, the sensitivity of the Stille coupling to steric effects was confirmed. Besides providing a variety of building blocks for retinoid synthesis, the study highlights some trends that might be useful for the application of the Stille reaction to the synthesis of unsubstituted conjugated polyenes.     

Thienoisoindigo‐based small molecules and narrow bandgap polymers synthesized via C–H direct arylation coupling

Thienoisoindigo (TIIG) has emerged as an attractive building block for high‐performance organic optoelectronic devices. Here we report the first synthesis of a series of π‐conjugated TIIG‐based small molecules and alternating copolymers via direct C–H arylation, which enables the efficient synthesis without use of flammable and toxic orgametallic reagents in fewer steps compared Suzuki and Stille coupling. The direct arylation coupling between TIIG and two respective mono‐bromo aryl reactants clearly shows that the α‐H is more reactive than the β‐H in the thiophene unit of TIIG. The high regioselectivity of TIIG monomer warrants the successful synthesis of high‐quality alternating copolymers with minimal structural defects. PTIIG‐BT polymer synthesized via direct arylation polymerization (DAP) showed comparable molecular weight and hole mobility than the same polymer previously synthesized via Suzuki coupling. Moreover, the two new polymers (PTIIG‐TF and PTIIG‐2FBT) synthesized via DAP showed hole mobility up to 10^?3 cm² V^?1 s^?1 in FET devices fabricated and tested under ambient conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2015–2031     

Studies in the Total Synthesis of Himastatin: A Revision of the Stereochemical Assignment

A stereoisomer of the natural product and not himastatin, an unusual dimeric depsipeptide with promising antibiotic and antitumor properties, was obtained from pyrroloindoline anti-cis- 1 . This result led to a revision of the proposed stereostructure. The new stereostructure was confirmed by the total synthesis, which involves stereoselective access to the pyrroloindoline syn-cis- 1 and the 5-hydroxypiperazic acid subunit and features a Stille coupling for the formation of the central carbon–carbon bond.     

Short communication: Stille coupling reactions of functionalized triorganotin halides

Convenient conditions for the Stille coupling of halide‐bearing triorganotin compounds, which do not normally react under typical Stille reaction conditions, are presented. The coupling of vinylstannanes with allyl bromide using palladium(II) catalysis is accomplished under fluoride assistance to give the substituted 2,5‐hexadien‐1‐ols in Z‐configuration. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis of D‐π‐A‐π type benzodithiophene‐quinoxaline copolymers by direct arylation and their application in organic solar cells

Conjugated copolymers based on benzodithiophene (BDT) derivatives and thiophene‐quinoxaline‐thiophene (TQT) segments represent an efficient class of light harvesting materials for organic photovoltaic (OPV) applications. Commonly, BDT‐TQT copolymers are synthesized by Stille cross‐coupling polymerization. In this study, alkoxy and thienyl functionalized alternating BDT‐alt‐TQT copolymers are synthesized by direct arylation polymerization (DArP), using Ozawa conditions. An extensive optimization of the reaction conditions such as the catalytic system, solvent, temperature, base, and the concentration of the catalyst is accomplished. The optical and electrochemical properties of the copolymers obtained by DArP are compared to the reference polymers synthesized by Stille cross‐coupling polymerization. Finally, the optimized BDT‐alt‐TQT copolymers are incorporated into organic solar cells as electron donors. The solar cells of the DArP copolymers exhibit power conversion efficiencies up to 80% (rel.) of their Stille cross coupling analogues. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1457–1467     

Development in Synthesis,Electrochemistry, LB Moieties of Phenothiazine Based Units

A convenient and higher yielding synthetic route to N‐alkyl‐bis(thiophene)phenothiazine derivatives is reported and their aggregation, electrochemical properties and polymerization are characterized. The key step in the synthesis of this group of compounds has been the Stille type coupling reaction between the N‐alkyldibromophenothiazine and tin derivatives of thiophene as the best way for preparation of conjugated N‐alkylphenothiazine derivatives. For this group of compounds we also present an electrochemical polymerization effect and widely adopted approach to prepare structurally ordered thin, electroconducting films by Langmuir–Blodgett technique.     

Direct Heteroarylation versus Stille Polycondensation Reaction for the Synthesis of TQ1 Conjugated Polymer

We report a facile synthesis of the well‐known and highly promising conjugated polymer TQ1 using eco‐friendly direct heteroarylation reaction. Optimization of the reaction conditions yielded the target polymer with good optoelectronic and charge‐transport characteristics. The TQ1 polymer obtained in the direct heteroarylation reaction delivered power conversion efficiency of ～5% in organic bulk heterojunction solar cells, which matches well the characteristics of the reference devices assembled using TQ1 batch synthesized via conventional Stille polycondensation reaction. The obtained results highlight the potential of the direct heteroarylation reaction as an efficient and environment‐friendly alternative to Stille cross‐coupling in the design of high‐quality semiconductor materials for organic electronics. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 776–782     

4-Bromomethyl-2-chlorooxazole--a versatile oxazole cross-coupling unit for the synthesis of 2,4-disubstituted oxazoles

The synthesis of the novel oxazole building block, 4-bromomethyl-2-chlorooxazole, and its palladium-catalysed cross-coupling reactions to make a range of 2,4-disubstituted oxazoles, is described. Selectivity for the 4-bromomethyl position is observed, with Stille coupling effected in good to excellent yields, or Suzuki coupling in moderate yields, to provide a range of 4-substituted-2-chlorooxazoles. Subsequent coupling at the 2-chloro-position can be achieved through either Stille or Suzuki reactions in excellent yields.     

Asymmetric total synthesis of (-)-mycothiazole

[structure: see text] In this Letter we describe the first total synthesis of mycothiazole, a polyketide thiazole from a marine sponge. Key steps include our CMD oxidation for the conversion of thiazolidine 11 to thiazole 12 and the Nagao acetate aldol reaction of 5 with aldehyde 4 to construct the chiral secondary alcohol. The skipped diene was constructed by the standard Stille coupling, and the conjugated diene was synthesized by lithium(I)- and copper(I)-mediated Stille coupling.     

Halogenated 2'-chlorobithiazoles via Pd-catalyzed cross-coupling reactions

Halogenated bithiazoles allow facile further functionalization and are, therefore, suitable intermediates for the synthesis of compounds with interesting biological activity or material science properties. The applicability of three coupling methods (Negishi, Suzuki, and Stille) for the synthesis of the title compounds was compared. The Negishi method proved to be troublesome, and side reactions were predominant. The synthesis of the first thiazoleboronic acid ester offered a new method for the formation of bithiazoles, not generally applicable so far. The lower toxicity compared to that of tin organyls make this method an approach with interesting perspectives. The Stille coupling proved to be superior to the other methods and enabled the synthesis of the title compounds with diverse connectivity.     

Tandem Stille/Suzuki-Miyaura coupling of a hetero-bis-metalated diene. Rapid, one-pot assembly of polyene systems

[structure: see text]. The synthesis of a hetero-bis-metallo 1,3-butadiene is reported, and its use as an orthogonal Stille and Suzuki-Miyaura coupling partner is detailed. The tin/boron diene participated successfully in a one-pot, sequential Stille and Suzuki-Miyaura coupling protocol, and its utility was demonstrated in the two-step construction of the pentaene side chain of the Fusarium metabolite lucilactaene.     

An Expedient Total Synthesis of Chivosazole F: an Actin‐Binding Antimitotic Macrolide from the Myxobacterium Sorangium Cellulosum

A unified strategy for the chemical synthesis of the chivosazoles is described. This strategy is based on two closely related approaches involving the late‐stage installation of the isomerization‐prone (2Z ,4E ,6Z ,8E )‐tetraenoate motif, and an expedient fragment‐assembly procedure. The result is a highly convergent total synthesis of chivosazole F through the orchestration of three mild Pd/Cu‐mediated Stille cross‐coupling reactions, including the use of a one‐pot, site‐selective, three‐component process, in combination with controlled installation of the requisite alkene geometry.     

Highly active palladium catalysts supported by bulky proazaphosphatrane ligands for Stille cross-coupling: coupling of aryl and vinyl chlorides, room temperature coupling of aryl bromides, coupling of aryl triflates, and synthesis of sterically hindered biaryls

A family of proazaphosphatrane ligands [P(RNCH2CH2)2N(R'NCH2CH2): R = R' = i-Bu, 1; R = Bz, R' = i-Bu, 3; R = R' = Bz, 4] for palladium-catalyzed Stille reactions of aryl chlorides is described. Catalysts derived from ligands 1 and 4 efficiently catalyze the coupling of electronically diverse aryl chlorides with an array of organotin reagents. The catalyst system based on the ligand 3 is active for the synthesis of sterically hindered biaryls (di-, tri-, and tetra-ortho substituted). The use of ligand 4 allows room-temperature coupling of aryl bromides and it also permits aryl triflates and vinyl chlorides to participate in Stille coupling.     

Total synthesis of leustroducsin B via a convergent route

Total synthesis of leustroducsin B was achieved via a convergent route, which includes Julia coupling reaction of segment A with segment B followed by Stille coupling reaction of segment C.     

Total Synthesis of the Protected Aglycon of Fidaxomicin (Tiacumicin B,Lipiarmycin A3)

Fidaxomicin, also known as tiacumicin B or lipiarmycin A3, is a novel macrocyclic antibiotic that is used in hospitals for the treatment of Clostridium difficile infections. This natural product has also been shown to have excellent bactericidal activity against multidrug‐resistant Mycobacterium tuberculosis. In spite of its attractive biological activity, no total synthesis has been reported to date. The enantioselective synthesis of the central 18‐membered macrolactone is reported herein. The key reactions include ring‐closing metathesis between a terminal olefin and a dienoate moiety for macrocyclization, a vinylogous Mukaiyama aldol reaction, and a Stille coupling reaction of sterically demanding substrates. The retrosynthesis involves three medium‐sized fragments, thus leading to a flexible yet convergent synthetic route.     

A new entry to the synthesis of 2,3-disubstituted indoles

[reaction: see text] The Stille coupling of N-acyl-2-iodoanilines with the 1-(tributylstannyl)-1-substituted allenes affected the successive one-step formation of the 2-methyl-3-substituted indoles. Alternatively, the other type of 2-alkyl-3-substituted indoles could be synthesized in a one-pot operation, which consists of the Stille coupling reaction with the 1-(tributylstannyl)-1,3-disubstituted allenes, followed by TBAF treatment. This procedure could be applied to the synthesis of indomethacin.