Progress on transition metal catalyzed asymmetric hydroesterification, hydrocarboxylation, and hydroamidation reactions of olefins.

Hydrocarboxylation, hydroesterification, and hydroamidation of olefins are fundamental transformations in organic synthesis. Asymmetric processes for these transformations provide an effective and straightforward approach to optically active carboxylic acids and their derivatives, which are highly useful compounds in pharmaceuticals, materials, fine chemicals, etc. This review provides a brief summary of the development of asymmetric hydroesterification, hydrocarboxylation, and hydroamidation with CO and its surrogates.

A facile copper(i)-catalyzed homo-coupling of indanone derivatives using diaziridinone under mild conditions.

A novel and efficient Cu(i)-catalyzed homo-coupling of indanone derivatives using diaziridinone as an oxidant is described. A variety of 1,4-dicarbonyl compounds bearing two adjacent quaternary stereocenters were obtained in high yields with high diastereoselectivities via a base-free and operationally simple process under mild reaction conditions.

An Effective Pd-Catalyzed Regioselective Hydroformylation of Olefins with Formic Acid.

An effective palladium-catalyzed regioselective hydroformylation of olefins with formic acid is described. The ligand plays a crucial role in directing the reaction pathway. Linear aldehydes can be obtained in up to 93% yield with >20:1 regioselectivity using 1,3-bis(diphenylphosphino)propane (dppp) as the ligand. The reaction process is operationally simple and requires no syngas.

A Facile Approach to Optically Active Hydroquinoline-2-carboxylates by a One-Pot Asymmetric Michael/Transamination/Cyclization Process.

An efficient one-pot synthesis of optically active hydroquinoline-2-carboxylates from 1,3-cyclohexanediones, ß,γ-unsaturated α-keto ester, and benzylamine in the presence of a chiral base catalyst and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with good diastereoselectivity and high enantioselectivity is described. The reaction proceeds by a sequential asymmetric Michael/transamination/cyclization process.

Pd-Catalyzed regioselective hydroesterification of 2-allylphenols to seven-membered lactones without external CO gas.

Effective Pd-catalyzed regioselective hydroesterification of 2-allylphenols with phenyl formate is described. A variety of seven-membered lactones can be obtained in good yields under mild conditions without the use of toxic CO gas.

Progress in asymmetric biomimetic transamination of carbonyl compounds.

Transamination of α-keto acids with transaminases and pyridoxamine phosphate is an important process to form optically active α-amino acids in biological systems. Various biomimetic transamination systems have been developed for carbonyl compounds including α-keto acid derivatives, fluoroalkyl ketones, and unactivated ketones with chiral vitamin B6 analogues, artificial transaminase mimics, chiral nitrogen sources, and chiral catalysts. This review provides a brief summary of this area.

Catalytic diamination of olefins via N-N bond activation.

CONSPECTUS: Vicinal diamines are important structural motifs present in various biologically and chemically significant molecules. Direct diamination of olefins provides an effective approach to this class of compounds. Unlike well-established oxidation processes such as epoxidation, dihydroxylation, and aminohydroxylation, direct diamination of olefins had remained a long-standing challenge and had been less well developed. In this Account, we summarize our recent studies on Pd(0)- and Cu(I)-catalyzed diaminations of olefins using di-tert-butyldiaziridinone and its related analogues as nitrogen sources via N-N bond activation. A wide variety of imidazolidinones, cyclic sulfamides, indolines, imidazolinones, and cyclic guanidines can be obtained from conjugated dienes and terminal olefins. For conjugated dienes, the diamination proceeds regioselectively at the internal double bond with the Pd(0) catalyst. Mechanistic studies show that the diamination likely involves a four-membered Pd(II) species resulting from the insertion of Pd(0) into the N-N bond of di-tert-butyldiaziridinone. Interestingly, the Cu(I)-catalyzed process occurs regioselectively at either the terminal or internal double bond depending on the reaction conditions via two mechanistically distinct pathways. The Cu(I) catalyst cleaves the N-N bond of di-tert-butyldiaziridinone to form a Cu(II) nitrogen radical and a four-membered Cu(III) species, which are likely in rapid equilibrium. The Cu(II) nitrogen radical and the four-membered Cu(III) species lead to the terminal and internal diamination, respectively. Terminal olefins are effectively C-H diaminated at the allylic and homoallylic carbons with Pd(0) as catalyst and di-tert-butyldiaziridinone as nitrogen source, likely involving a diene intermediate generated in situ from the terminal olefin via formation of a π-allyl Pd complex and subsequent ß-hydride elimination. When di-tert-butylthiadiaziridine 1,1-dioxide is used as nitrogen source, cyclic sulfamides are installed at the terminal carbons via a dehydrogenative diamination process. When α-methylstyrenes (lacking homoallylic hydrogens) react with Pd(0) and di-tert-butyldiaziridinone, spirocyclic indolines are formed with generation of four C-N bonds and one spiro quaternary carbon via allylic and aromatic C-H amination. With Cu(I) catalysts, various terminal olefins can be effectively diaminated at the double bonds using di-tert-butyldiaziridinone, di-tert-butylthiadiaziridine 1,1-dioxide, and 1,2-di-tert-butyl-3-(cyanimino)-diaziridine as nitrogen sources, giving a variety of imidazolidinones, cyclic sulfamides, and cyclic guanidines in good yields, respectively. In the case of monosubstituted olefins using di-tert-butyldiaziridinone as nitrogen source, the resulting diamination products (imidazolidinones) are readily dehydrogenated under the reaction conditions, leading to the corresponding imidazolinones in good yields. Esters can also be diaminated to form the corresponding hydantoins with di-tert-butyldiaziridinone in the presence of a Cu(I) catalyst. A radical mechanism is likely to be operating in these Cu(I)-catalyzed reaction processes. Asymmetric processes have also been developed for the Pd(0)- and Cu(I)-catalyzed diamination reactions. Biologically active compounds such as (+)-CP-99,994 and Sch 425078 have been synthesized via the diamination processes. The diamination reactions described herein provide efficient methods to access a wide variety of vicinal diamines from readily available olefins and show great potential for synthetic applications.

Catalytic Asymmetric Bromination of Unfunctionalized Olefins with H2O as a Nucleophile.

The dimeric cinchona alkaloid (DHQD)2 PHAL is used to catalyze an effective asymmetric bromohydroxylation of unfunctionalized olefins with H2 O as nucleophile an N-bromobenzamide as a bromine source. A variety of optically active bromohydrins are formed with up to 88 % ee.

An atom-economic approach to carboxylic acids via Pd-catalyzed direct addition of formic acid to olefins with acetic anhydride as a co-catalyst.

An effective Pd-catalyzed hydrocarboxylation of olefins using formic acid with acetic anhydride as a co-catalyst is described. A variety of carboxylic acids are obtained in good yields with high regioselectivities under mild reaction conditions without the use of toxic CO gas.

A facile approach to ß-amino acid derivatives via palladium-catalyzed hydrocarboxylation of enimides with formic acid.

An effective Pd(0)-catalyzed hydrocarboxylation of enimides with formic acid in the presence of a catalytic amount of HCOOPh is described. A variety of ß-amino acid derivatives are obtained in good yields with high regioselectivities without using external toxic CO gas.

Enantioselective 6-endo bromoaminocyclization of 2,4-dienyl N-tosylcarbamates catalyzed by a chiral phosphine oxide-Sc(OTf)3 complex. A dramatic additive effect.

An effective enantioselective 6-endo bromoaminocyclization of 2,4-dienyl N-tosylcarbamates catalyzed by a chiral phosphine oxide-Sc(OTf)3 complex is described. A wide variety of optically active 5-bromo-1,3-oxazinan-2-ones containing various functional groups can be obtained in 61-91% yields and 92-99% ees. An additive, such as NaCl, has been found to be crucial for the reaction process.

A palladium-catalyzed enantioselective hydroesterification of alkenylphenols with phenyl formate. A facile approach to optically active dihydrocoumarins.

An effective palladium-catalyzed enantioselective hydroesterification of alkenylphenols with phenyl formate as a CO source is described. A variety of optically active dihydrocoumarins can be obtained in generally high yields with up to 91% ee.

Cu(I)-catalyzed sequential diamination and dehydrogenation of terminal olefins: a facile approach to imidazolinones.

Diamination of olefins presents a powerful strategy to access vicinal diamines. During the last decade, metal-catalyzed diamination of olefins has received considerable attention. This study describes an efficient sequential diamination and dehydrogenation process of terminal olefins with CuBr as catalyst and di-tert-butyldiaziridinone as nitrogen source, providing a facile and viable approach to a variety of imidazolin-2-ones, which are important structural motifs present in various biologically active molecules.

Synthesis of optically active deuterated primary amines via reduction of N-tert-butanesulfinyl aldimines.

Optically active deuterated primary amines have been obtained with 78-98% ee's from chiral N-tert-butanesulfinyl aldimines via reduction with N-Selectride and subsequent alcoholysis.

A facile approach to spirocyclic 2-azido indolines via azidation of indoles with ceric ammonium nitrate.

This paper describes azidation of indoles with NaN3 and ceric ammonium nitrate (CAN), giving a variety of spirocyclic 2-azido indolines in good yields and moderate diastereoselectivities.

Organocatalytic synthesis of optically active ß-branched α-amino esters via asymmetric biomimetic transamination.

This paper describes an efficient asymmetric biomimetic transamination of α-keto esters with a quinine-derived chiral base as the catalyst, giving a variety of ß-branched α-amino esters in 50-96% yield and 87-95% ee.

Palladium(0)-catalyzed Heck reaction/C-H activation/amination sequence with diaziridinone: a facile approach to indolines.

Indolines are important moieties present in various biologically significant molecules and have attracted considerable attention in synthetic chemistry. This paper describes a Heck reaction/C-H activation/amination sequence for forming indolines using di-tert-butyldiaziridinone. The reaction process likely proceeds via a pallada(II)cycle, which is converted into an indoline by oxidative addition to the diaziridinone and two subsequent C-N bond formations.

Pd-Catalyzed Regioselective Hydrocarboxylation of Alkyl Terminal Olefins with Oxalic Acid.

A Pd-catalyzed regioselective hydrocarboxylation of alkyl terminal olefins with oxalic acid is described. A wide variety of linear carboxylic acids can be readily obtained in good yields and high l/b (linear/branched) ratios with Pd2(dba)3 and (p-ClPh)3P under mild conditions. The reaction process is operationally simple and requires no handling of toxic CO. In addition, branched carboxylic acids can also be formed in good regioselectivities with PdCl2 and (2',6'-dimethoxy-[1,1'-biphenyl]-2-yl)diphenylphosphine (L1).

Enantioselective bromoaminocyclization of allyl N-tosylcarbamates catalyzed by a chiral phosphine-Sc(OTf)3 complex.

An effective enantioselective bromoaminocyclization of allyl N-tosylcarbamates catalyzed by a chiral phosphine-Sc(OTf)3 complex is described. A wide variety of optically active oxazolidinone derivatives containing various functional groups can be obtained with high enantioselectivities.

A facile copper(I)-catalyzed homocoupling of terminal alkynes to 1,3-diynes with diaziridinone under mild conditions.

A novel and efficient Cu(I)-catalyzed oxidative homocoupling of terminal alkynes with diaziridinone as an oxidant is described. Various terminal alkynes can be transformed into the corresponding 1,3-diynes in good yields. The reaction process is base-free, operationally simple, and amenable to the gram scale.