Scope and limitations of the Heck–Matsuda-coupling of phenol diazonium salts and styrenes: a protecting-group economic synthesis of phenolic stilbenes

Abstract

4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4'-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior.

Acetamidoarenediazonium Salts: Opportunities for Multiple Arene Functionali­zation

“…Remarkably, in acetonitrile basic conditions were found to be advantageous, giving p ‐ 11aa in quantitative yield, whereas only a moderate yield of 41 % was observed in the absence of a base (see the Supporting Information). These results are to some extent in line with observations previously published by us on Matsuda–Heck reactions of arenediazonium salts bearing hydroxy or methoxy substituents in the meta or para position relative to the diazonium group 22,25. We reason that in this and in the present case the electron‐donating substituent has an overall beneficial effect on the Pd‐catalyzed coupling by enhancing the electron density on the ipso ‐C and the diazonium group.…”

“…The electron‐deficient styrene 10g was the most reactive coupling partner, giving stilbene p ‐ 11ag in quantitative yield (Entry 13). In this particular case, inseparable mixtures of E and Z isomers were obtained irrespective of the conditions; this has previously also been observed by us for Matsuda–Heck reactions between p ‐nitrostyrene ( 10g ) and other diazonium salts 25…”

“…Although first described in the late 1970s, by Matsuda and co‐workers,14 the potential for use of arenediazonium salts as electrophilic arylating agents for Pd‐catalyzed coupling reactions has only recently been more intensively investigated 15–20. Our main contribution to the field is the development of a deacetylation/diazotization (DD) sequence for the one‐flask synthesis of arenediazonium salts from acetanilides,21–25 and the extension of this synthesis through a Pd‐catalyzed coupling or cross‐coupling reaction to a deacetylation/diazotization/coupling (DDC) sequence 26. In previous contributions we demonstrated that DD and DDC sequences have the potential to broaden the scope and synthetic utility of oxidative Pd‐catalyzed C–H activation reactions of the Fujiwara–Moritani type, because they allow efficient recycling of the catalyst‐directing acetamido group by conversion into a diazonium leaving group 27,28…”

A Highly Stereoselective and Efficient Catalytic Approach for the Synthesis of trans‐Stilbene–Arenes as π‐Conjugated Materials

“…This is the first report of a selective method for the effective synthesis of (E)-arylene stilbenes consisting of differently sized aromatic parts without (20)(21)(22)(23) or with heteroatoms [such as sulfur (24) and nitrogen (25)] or a metallocene (26). Complex 1 is an efficient homogeneous catalyst in the Suzuki coupling of vinylphenyl boronic acid with bromoarenes.…”

“…[14] Organozinc halides react with carbonyl compounds in the presence of the palladium(II) complex PdCl 2 (PPh 3 ) 2 and a silylating agent to give the corresponding (E)-stilbenes in good-to-excellent yields under mild conditions. [17][18][19][20] The metathesis transformations used extensively in total synthesis include ring-closing metathesis (RCM), cross-metathesis (CM), ring-opening metathesis (ROM), and ring-opening metathesis polymerization (ROMP). [15,16] The formation of carbon-carbon bonds is of vital importance in preparative organic processes from the synthesis of molecular models to macromolecular and nanomaterials science.…”