Synthesis of Phenylpropanoids via Matsuda–Heck Coupling of Arene Diazonium Salts

Abstract

The Pd-catalyzed Heck-type coupling (Matsuda-Heck reaction) of electron rich arene diazonium salts with electron deficient olefins has been exploited for the synthesis of phenylpropanoid natural products. Examples described herein are the naturally occurring benzofurans methyl wutaifuranate, wutaifuranol, wutaifuranal, their 7-methoxy derivatives, and the O-prenylated natural products boropinols A and C.

Iterative Arylation of Itaconimides with Diazonium Salts through Electrophilic Palladium Catalysis: Divergent β-H-Elimination Pathways in Repetitive Matsuda–Heck Reactions

“…Although several modifications and improvements, including a catalytic variant, 18 have been published since the original report, 6,[19][20][21][22][23] some disadvantages of this approach remain: in general, elevated temperatures and protic solvents are required to achieve useful levels of conversion, which may affect hydrolytic stability of the succinimide structure; 24 the required benzaldehydes are sometimes prone to oxidation and need to be purified beforehand; other carbonyl groups that may also undergo Wittig olefination reactions are not tolerated; the inevitable formation of stoichiometric amounts of phosphine oxides can hamper product isolation and purification if the 3-arylmethylidene pyrrolidine-2,5-diones have similar polarity. In continuation of our previous investigations [25][26][27] into the development and application of Matsuda-Heck reactions, 28 i. e. the Pd-catalyzed Heck-type coupling of arene diazonium salts with alkenes, [29][30][31][32][33][34][35][36] we wondered whether an alternative approach to 3-arylmethylidene pyrrolidine-2,5-diones exo-1 that starts from itaconimides 5 and stable and isolable arene diazonium salts 6 might be a competitive or even advantageous alternative to the phospha-Michael-addition / Wittig-olefination approach. Important questions to be answered in this context are: will the final -H-elimination step 36 leading to the liberation of the coupling products proceed exo-or endo-selectively (i. e. to exo-1 or to endo-1), or to a mixture of exoand endo-isomers?…”

Benign Arylations of Dimethyl Itaconate via Heck–Matsuda Reaction Utilizing in‐Situ Generated Palladium on Aluminum Oxide

“…The Heck–Matsuda reaction, which has provided valuable services in organic synthesis over the past decades, opens up a way out of the limitations of the previous presentation methods described above …”

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

“…RCM of enol ethers [57–58] 10 under the same conditions used for the synthesis of the oxepino-annellated coumarins 11 gave furanocoumarins 3 in excellent yields (Table 2). Furanocoumarins 3a (angelicin or isopsoralen, Table 2, entry 1) [11–12] and 3c (sphondin, Table 2, entry 3) [59–60] are natural products.…”