Intramolecular Alkoxycyanation and Alkoxyacylation Reactions: New Types of Alkene Difunctionalizations for the Construction of Oxygen Heterocycles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93742/1/10224_ftp.pd

Carbon−Heteroatom and Carbon−Carbon Bond‐Forming Reactions: Special Issue in Honor of the 2019 Wolf Prize Laureates in Chemistry, Professors Stephen L. Buchwald and John F. Hartwig

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154904/1/ijch202000013_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154904/2/ijch202000013.pd

Desymmetrization of meso ‐2,5‐Diallylpyrrolidinyl Ureas through Asymmetric Palladium‐Catalyzed Carboamination: Stereocontrolled Synthesis of Bicyclic Ureas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99614/1/9247_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/99614/2/anie_201302720_sm_miscellaneous_information.pd

Stereocontrolled Synthesis of Amino‐Substituted Carbocycles by Pd‐Catalyzed Alkene Carboamination Reactions

Amino‐substituted alkylidenecyclopentanes were synthesized through a stereoselective intermolecular Pd‐catalyzed alkene carboamination reaction between alkenyl triflates bearing a pendant alkene and exogenous amine nucleophiles. The reactions are effective with a range of different substrate combinations, and proceed with generally high diastereoselectivity. Use of (S)‐tBuPhox as the ligand in reactions of achiral substrates provides enantioenriched products with up to 98.5:1.5 e.r.Adding amines: The palladium‐catalyzed coupling of amines with enol triflates derived from 2‐allylcycloalkanones provides substituted alkylidenecyclopentylamine derivatives in good yield with high levels of stereoselectivity. Achiral substrates are transformed with up to 98.5:1.5 e.r.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136662/1/chem201700466_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136662/2/chem201700466.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136662/3/chem201700466-sup-0001-misc_information.pd

Palladium‐Catalyzed Alkene Carboamination Reactions of Electron‐Poor Nitrogen Nucleophiles

Modified reaction conditions that facilitate Pd‐catalyzed alkene carboamination reactions of electron‐deficient nitrogen nucleophiles are reported. Pent‐4‐enylamine derivatives bearing N‐tosyl or N‐trifluoroacetyl groups are coupled with aryl triflates to afford substituted pyrrolidines in good yield. These reactions proceed via a mechanism involving anti‐aminopalladation of the alkene, which differs from previously reported analogous reactions of N‐aryl‐ and N‐Boc‐pentenylamines. The application of these conditions to a formal synthesis of (±)‐aphanorphine is also described.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112250/1/2339_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112250/2/adsc_201500334_sm_miscellaneous_information.pd

Influence of Catalyst Structure and Reaction Conditions on anti ‐ versus syn ‐Aminopalladation Pathways in Pd‐Catalyzed Alkene Carboamination Reactions of N ‐Allylsulfamides

The Pd‐catalyzed coupling of N ‐allylsulfamides with aryl and alkenyl triflates to afford cyclic sulfamide products is described. In contrast to other known Pd‐catalyzed alkene carboamination reactions, these transformations may be selectively induced to occur by way of either anti ‐ or syn ‐aminopalladation mechanistic pathways by modifying the catalyst structure and reaction conditions. A constructive approach : A concise, efficient approach has led to the synthesis of cyclic sulfamides by using Pd‐catalyzed alkene carboamination reactions of N ‐allylsulfamides (see picture; OTf=triflate, RuPhos=2‐dicyclohexylphosphino‐2′,6′‐diisopropoxybiphenyl, X‐phos=2‐dicyclohexylphosphino‐2′,4′,6′‐triisopropylbiphenyl). The mechanism of these transformations is highly dependent on the catalyst structure and reaction conditions. The reactions can be induced to proceed selectively through either syn ‐ or anti ‐aminopalladation pathways under appropriate conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107505/1/chem_201402258_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/107505/2/8782_ftp.pd

Pd‐Catalyzed C−C, C−N, and C−O Bond‐Forming Difunctionalization Reactions of Alkenes Bearing Tethered Aryl/Alkenyl Triflates

Over the past few years our group has described a new type of alkene difunctionalization reaction in which aryl or alkenyl triflates bearing tethered alkenes are coupled with various nucleophiles to afford carbocyclic products. The products are formed in moderate to good chemical yield, with generally high levels of stereoselectivity. Our progress to date in this area, which includes reactions of amine, alcohol, enolate, and indole nucleophiles, is described in this review.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154890/1/ijch201900108_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154890/2/ijch201900108.pd

Development of Enantioselective Palladium‐Catalyzed Alkene Carboalkoxylation Reactions for the Synthesis of Tetrahydrofurans

The Pd‐catalyzed coupling of γ‐hydroxyalkenes with aryl bromides affords enantiomerically enriched 2‐(arylmethyl)tetrahydrofuran derivatives in good yield and up to 96:4 e.r. This transformation was achieved through the development of a new TADDOL/2‐arylcyclohexanol‐derived chiral phosphite ligand. The transformations are effective with an array of different aryl bromides, and can be used for the preparation of products bearing quaternary stereocenters.The construction of enantiomerically enriched tetrahydrofurans is accomplished by asymmetric Pd‐catalyzed cross‐coupling reactions between γ‐hydroxyalkenes and aryl bromides. Use of a palladium catalyst supported by a new TADDOL‐derived chiral phosphite ligand provides the tetrahydrofuran products in good yield with up to 96:4 e.r. (see scheme).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115961/1/anie_201506884_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115961/2/13390_ftp.pd

Simple, Efficient Catalyst System for the Palladium-Catalyzed Amination of Aryl Chlorides, Bromides, and Triflates

Palladium complexes supported by (o-biphenyl)P(t-Bu)_2 (3) or (o-biphenyl)PCy_2 (4) are efficient catalysts for the catalytic amination of a wide variety of aryl halides and triflates. Use of ligand 3 allows for the room-temperature catalytic amination of many aryl chloride, bromide, and triflate substrates, while ligand 4 is effective for the amination of functionalized substrates or reactions of acyclic secondary amines. The catalysts perform well for a large number of different substrate combinations at 80−110 °C, including chloropyridines and functionalized aryl halides and triflates using 0.5−1.0 mol % Pd; some reactions proceed efficiently at low catalyst levels (0.05 mol % Pd). These ligands are effective for almost all substrate combinations that have been previously reported with various other ligands, and they represent the most generally effective catalyst system reported to date. Ligands 3 and 4 are air-stable, crystalline solids that are commercially available. Their effectiveness is believed to be due to a combination of steric and electronic properties that promote oxidative addition, Pd−N bond formation, and reductive elimination

Hydrogen-Based Activity Enhancement in Sediment Cultures and Intact Sediments

The potential for hydrogen gas to stimulate microbial respiratory activity in sediments was investigated. Cell elutions from Passaic River (NJ), San Diego Bay (CA), and Marine Harbor sediments were amended with hydrogen gas to evaluate its impact on microbial activity measured by intracellular reduction of 5-cyano-2,3-ditolyl tetrazolium chloride (CTC). The transferability of this approach to sediment slurries and static sediment columns was evaluated based on microbial activity enhancement in Marine Harbor sediments. Results indicate that microbial activity can be increased by a factor of 2–3 at a threshold hydrogen concentration range (0.5 to 1.5 μM). Terminal restriction fragment (T-RF) length polymorphism analysis indicated that the community response to hydrogen resulted in the emergence of previously recessive populations. The causal relationship between hydrogen amendment and an increase in CTC-active cells was most likely due to community structure shifts, as evidenced by the emergence of new T-RFs (19% of total) at hydrogen concentrations above 1.5 μM. No RF was dominant within this emergent group, and no chlororespirers were detected within this group, the latter probably due to the lack of enrichment of halogenated compounds. Nevertheless, the transferability of the observed relationship between hydrogen gas amendment and microbial activity to complex sediment samples suggests a promising remedial strategy for in place contaminated estuarine sediments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63230/1/ees.2006.0078.pd