Iron(III) Chloride Catalyzed Oxidative Coupling Reaction of 1,2‐Diarylethylene Derivatives

Abstract

A nontoxic FeCl 3 catalyzed intramolecular oxidative coupling reaction was developed for mild synthesis of a series of phenanthrenes with different substituents. The method involves cross dehydrogenative coupling of a variety of 1,2-diarylethylene derivatives with di-tert-butylperoxide (DTBP) as a sole oxidant at room temperature in CH 2 Cl 2 /TFA (9∶1 V/V) to yield phenanthrenes in good to excellent yields.

Iron Catalysis in Organic Synthesis

“…They presented 15 examples for this transformation which led to phenanthrenes in excellent yields. 563 Katsuki and Egami developed an efficient iron-catalyzed asymmetric homocoupling of 2-naphthols using atmospheric oxygen as oxidant (Scheme 298). 564 They employed chiral salanÀiron complexes for this transformation affording 3,3 0disubstituted 1,1 0 -binaphthalene-2,2 0 -diols in high yields and with high enantioselectivities.…”

“…More recently, Yang and co-workers demonstrated that the same iron(III)-catalyzed cyclization can be achieved using di- tert -butyl peroxide instead of m CPBA as terminal oxidant in a mixture of dichloromethane and trifluoroacetic acid. They presented 15 examples for this transformation which led to phenanthrenes in excellent yields …”

Intramolecular Dehydrogenative Coupling of 2,3-Diaryl Acrylic Compounds: Access to Substituted Phenanthrenes

“…All starting materials were prepared according to the known literature procedure. 2,3-Diaryl acrylic acid derivatives were prepared by perking condensation of aromatic aldehyde with phenylacetic acid derivatives according to the reported procedure . Acrylic acid was converted into esters 4a , 4b , 4l – 4o , 4p , 4q , and corresponding nitrile 4k by a well known literature procedure.…”

“…To date, most of the procedures using aryls for obtaining phenanthrene rings have explored the use of many heavy metal reagents such as MoCl 5 /TiCl 4 , thallium­(III) trifluoroacetate, lead­(IV) tetraacetate, Ru (IV), early transition metal salts, e.g., vanadium oxytrifluoride (VOF 3 ) or vanadium oxy trichloride (VOCl 3 ), MnO 2 –BF 3 ·OEt 2 , iron­(III) chloride, and metal-free oxidants such as hypervalent iodine, phenyliodine­(III) bis­(trifluoroacetate) (PIFA), phenyliodine­(III) diacetate (PIDA), , DDQ/CH 3 SO 3 H, and photocyclization in the presence of iodine . Unfortunately, the poor substrate scope, average reaction yields, harsh reaction conditions, and high toxicity associated with the reagents limit the application of these methodologies.…”

Synthesis and study of structure of the iron chloride – polyvinylpyrrolidone complex

“…Iron (III) complexes are widely used as catalysts of many organic processes, because of the features of an electronic structure of iron in oxidized (d 5 ) and reduced (d 6 ) states, a possibility of regeneration by oxygen, high complexing ability and good solubility in organic solvents. Owing to interaction metal-ligand homogeneous catalysts on the basis of iron chloride (FeCl 3 ) have a high activity and selectivity in Michael reaction [1], allylation of aldehydes with allyltrimethylsilane [2], acetal-ene reaction [3], conversion of epoxides to acetonides [4], oxidative coupling reaction of 1,2-diarylethylene derivatives [5], synthesis of coumarins from phenols and β-ketoesters [6]. In turn, poly(N-vinyl-2-pyrrolidone) (PVP) is nontoxical, water-soluble and biologically compatible and therefore ecologically harmless polymeric ligand [7,8].…”