Pd-catalyzed intramolecular addition of active methylene compounds to alkynes with subsequent cross-coupling with (hetero)aryl halides

Abstract

A tandem cyclization/coupling of acetylenic active methylene compounds with aryl halides features broad scope and excellent functional group compatibility. Mechanistic studies identified 5-exo-dig cyclization as the rate limiting step.

Eco‐Friendly Methodology for the Formation of Aromatic Carbon–Heteroatom Bonds by Using Green Ionic Liquids

“…In details, anisole gave the expected p ‐bromoanisole with a good yield (Table 2, entry 1). This regioselective monobromination reaction is of particular relevance as bromoanisole finds numerous applications as an intermediate in synthetic chemistry, such as in the preparation of aryl 1,3‐diketones and as substrate in Suzuki and Heck coupling reactions [37–41] . 1,2‐ and 1,3‐dimethoxybenzene were brominated with satisfactory yields (Table 2, entries 2 and 3).…”

Tandem Pd-Catalyzed Cyclization/Coupling of Non-Terminal Acetylenic Activated Methylenes with (Hetero)Aryl Bromides

“…In most cases, better yields were observed for the reaction with electron-deficient aryl bromides. Change of the substituent at the alkyne terminus to ethyl or phenyl was also tolerated, although slightly lower yields were observed (leading to [33][34].…”

“…This strategy was first realized by Balme in the early 1990s for acetylenic keto esters and malonates with simple aryl iodides [30][31][32]. More recently, employing a catalyst based on a bulky, electron-rich monophosphine, we have solved one of the major limitations of the reaction, disclosing mild and functional group-tolerant conditions suitable for considerably less reactive (hetero)aryl bromides and chlorides [33,34]. However, one of the remaining challenges of both 5-exo-dig cycloisomerization and cyclization/coupling processes catalyzed by carbophilic Lewis acids is the low reactivity of substrates derived from internal alkynes.…”

Cross-coupling of aldehydes and α-bromophosphonates to modularly access α-substituted-β-ketophosphonates under dual nickel/photoredox catalysis

“…The thioether group (8) had no obvious influence on the reaction. The candidates with versatile functional groups such as protected alcohol (9), ester (10), or amide (11), which are widespread and can be converted to many other groups, can be employed to afford α-substituted-β-ketophosphonates in good yields. Heterocycle-containing aldehydes can be utilized as exemplified with compound 12.…”

“…However, comparatively, there are relatively very few methods to conveniently and directly obtain α-substituted-β-ketophosphonates (Scheme 1). Generally, they have to be prepared from β-ketophosphonates via enolization with strong bases and subsequent nucleophilic substitution with active alkyl halides 10 or via α-functionalization with a transition metal catalyst 11 (Scheme 1a). Despite several additional studies with sporadic examples of α-substituted-β-ketophosphonate formation, 12 apparently, a modular and facile method to deliver this type of product is still highly demanded.…”