Search for: All records

Pepper (Capsicumspp.) is one of the earliest cultivated crops and includes five domesticated species,C. annuumvar.annuum,C. chinense,C. frutescens,C. baccatumvar.pendulumandC. pubescens. Here, we report a pepper graph pan-genome and a genome variation map of 500 accessions from the five domesticatedCapsicumspecies and close wild relatives. We identify highly differentiated genomic regions among the domesticated peppers that underlie their natural variations in flowering time, characteristic flavors, and unique resistances to biotic and abiotic stresses. Domestication sweeps detected inC. annuumvar.annuumandC. baccatumvar.pendulumare mostly different, and the common domestication traits, including fruit size, shape and pungency, are achieved mainly through the selection of distinct genomic regions between these two cultivated species. Introgressions fromC. baccatumintoC. chinenseandC. frutescensare detected, including those providing genetic sources for various biotic and abiotic stress tolerances.

 

A highly selective palladium-catalyzed carbonylative arylation of weakly acidic benzylic C(sp 3 )–H bonds of azaarylmethylamines with aryl bromides under 1 atm of CO gas has been achieved. This work represents the first examples of use of such weakly acidic pronucleophiles in this class of transformations. In the presence of a NIXANTPHOS-based palladium catalyst, this one-pot cascade process allows a range of azaarylmethylamines containing pyridyl, quinolinyl and pyrimidyl moieties and acyclic and cyclic amines to undergo efficient reactions with aryl bromides and CO to provide α-amino aryl-azaarylmethyl ketones in moderate to high yields with a broad substrate scope and good tolerance of functional groups. This reaction proceeds via in situ reversible deprotonation of the benzylic C–H bonds to give the active carbanions, thereby avoiding prefunctionalized organometallic reagents and generation of additional waste. Importantly, the operational simplicity, scalability and diversity of the products highlight the potential applicability of this protocol. 

A novel, selective and high‐yielding palladium‐catalyzed carbonylative arylation of a variety of weakly acidic (pK_a25–35 in DMSO) benzylic and heterobenzylic C(sp³)−H bonds with aryl bromides has been achieved. This system is applicable to a range of pro‐nucleophiles for access to sterically and electronically diverse α‐aryl or α,α‐diaryl ketones, which are ubiquitous substructures in biologically active compounds. The Josiphos SL‐J001‐1‐based palladium catalyst was identified as the most efficient and selective, enabling carbonylative arylation with aryl bromides under 1 atm CO to provide the ketone products without the formation of direct coupling byproducts. Additionally, (Josiphos)Pd(CO)₂was identified as the catalyst resting state. A kinetic study suggests that the oxidative addition of aryl bromides is the turnover‐limiting step. Key catalytic intermediates were also isolated.

 

A novel, selective and high‐yielding palladium‐catalyzed carbonylative arylation of a variety of weakly acidic (pK_a25–35 in DMSO) benzylic and heterobenzylic C(sp³)−H bonds with aryl bromides has been achieved. This system is applicable to a range of pro‐nucleophiles for access to sterically and electronically diverse α‐aryl or α,α‐diaryl ketones, which are ubiquitous substructures in biologically active compounds. The Josiphos SL‐J001‐1‐based palladium catalyst was identified as the most efficient and selective, enabling carbonylative arylation with aryl bromides under 1 atm CO to provide the ketone products without the formation of direct coupling byproducts. Additionally, (Josiphos)Pd(CO)₂was identified as the catalyst resting state. A kinetic study suggests that the oxidative addition of aryl bromides is the turnover‐limiting step. Key catalytic intermediates were also isolated.

 

An umpolung 1,4‐addition of aryl iodides to enals promoted by cooperative (terpy)Pd/NHC catalysis was developed that generates various bioactive β,β‐diaryl propanoate derivatives. This system is not only the first reported palladium‐catalyzed arylation of NHC‐bound homoenolates but also expands the scope of NHC‐induced umpolung transformations. A diverse array of functional groups such as esters, nitriles, alcohols, and heterocycles are tolerated under the mild conditions. This method also circumvents the use of moisture‐sensitive organometallic reagents.

 

An umpolung 1,4‐addition of aryl iodides to enals promoted by cooperative (terpy)Pd/NHC catalysis was developed that generates various bioactive β,β‐diaryl propanoate derivatives. This system is not only the first reported palladium‐catalyzed arylation of NHC‐bound homoenolates but also expands the scope of NHC‐induced umpolung transformations. A diverse array of functional groups such as esters, nitriles, alcohols, and heterocycles are tolerated under the mild conditions. This method also circumvents the use of moisture‐sensitive organometallic reagents.

 

A straightforward method for the palladium‐catalyzed triarylation of heteroarylmethanes at the methyl group has been developed. The reaction works with a variety of aryl halides, enabling the rapid synthesis of triaryl(heteroaryl)methanes in moderate to excellent yields.

magnified image