Rhodium‐Catalyzed Hydroformylation of 1,1‐Disubstituted Allenes Employing the Self‐Assembling 6‐DPPon System

A rhodium‐catalyzed hydroformylation of 1,1‐disubstituted allenes is reported. Using a Rh^I/6‐DPPon catalyst system, one can obtain β,γ‐unsaturated aldehydes in high regio‐ and chemoselectivity. The Z‐configured product is formed with up to >95 % selectivity when unsymmetrically 1,1‐disubstituted allenes are submitted to the reaction conditions. This is the first time that these interesting building blocks are accessible by hydroformylation of allenes. The utility of this methodology is demonstrated by further transformations of one of the obtained products.     

Rhodium catalysed hydroformylation of unsaturated esters

Rhodium catalysed hydroformylation of unsaturated esters has been studied. A pronounced temperature dependence was observed on the regioselectivity and catalytic activity for these reactions, and under the appropriate conditions, it is possible to obtain preferentially either linear or quaternary products. A quaternary selective hydroformylation of methyl atropate to give 1,3-aldehydic esters has also been developed.     

CuI-catalyzed coupling reaction of beta-amino acids or esters with aryl halides at temperature lower than that employed in the normal Ullmann reaction. Facile synthesis of SB-214857

[reaction: see text] The CuI-catalyzed coupling reaction of aryl halides with beta-amino acids or beta-amino esters is completed at 100 degrees C in 48 h, which indicates that the structure of the beta-amino acid has an accelerating effect for the Ullmann-type aryl amination reaction. This coupling reaction can be used to prepare enantiopure N-aryl beta-amino acids. An efficient synthetic route to SB214857, a potent GPIIb/IIIa receptor antagonist, is developed using this method.     

Syngas‐Free Highly Regioselective Rhodium‐Catalyzed Transfer Hydroformylation of Alkynes to α,β‐Unsaturated Aldehydes

The hydroformylation of alkynes is a fundamental and important reaction in both academic research and industry. Conventional methods focus on the conversion of alkynes, CO, and H₂ into α,β‐unsaturated aldehydes, but they often suffer from problems associated with operation, regioselectivity, and chemoselectivity. Herein, we disclose an operationally simple, mild, and syngas‐free rhodium‐catalyzed reaction for the hydroformylation of alkynes via formyl and hydride transfer from an alkyl aldehyde. This synthetic method uses inexpensive and easy‐to‐handle n‐butyraldehyde to overcome the challenge posed by the use of syngas in traditional approaches and employs a commercially available catalyst and ligand to transform a broad range of internal alkynes, especially alkynyl‐containing complex molecules, into versatile stereodefined α,β‐unsaturated aldehydes with excellent chemo‐, regio‐, and stereoselectivity.     

A formal enantioselective acetate Mannich reaction: the nitro functional group as a traceless agent for activation and enantiocontrol in the synthesis of beta-amino acids

A two-step procedure involving the enantioselective addition of alpha-nitro esters to imines, followed by reductive denitration, provides a convenient new enantioselective synthesis of beta-amino acids. Specifically, beta-phenyl alanine derivatives with up to 98% ee are formed in good yield (64-88%) over two steps. The utility of the approach is demonstrated through the first enantioselective synthesis of the key beta-amino acid of (+)-chaenorhine.     

Kowalski ester homologation. application to the synthesis of beta-amino esters

The Kowalski ester homologation protocol has been applied to a representative range of alpha-amino esters to provide beta-amino esters with excellent levels of enantio- and diastereocontrol. A key feature of this chemistry is the nature of the N-protecting group that is employed.     

Combined Transition‐Metal‐ and Organocatalysis: An Atom Economic C3 Homologation of Alkenes to Carbonyl and Carboxylic Compounds

A combination of regioselective room‐temperature/ambient‐pressure hydroformylation (transition‐metal catalysis) and decarboxylative Knoevenagel reactions (organocatalysis) allowed for the development of an efficient, one‐pot C3 homologation of terminal alkenes to (E)‐α,β‐unsaturated acids and esters, (E)‐β,γ‐unsaturated acids, (E)‐α‐cyano acrylic acids, and α,β‐unsaturated nitriles. All reactions proceed under mild conditions, tolerate a variety of functional groups, and furnish unsaturated carbonyl compounds in good yields and with excellent regio‐ and stereocontrol. Further, an iterative C2 homologation of (E)‐α,β‐unsaturated carboxylic acids is possible through a combination of decarboxylative hydroformylation employing a supramolecular catalyst followed by decarboxylative Knoevenagel condensation with an organocatalyst.     

A sequential palladium-catalyzed alder-ene-reductive amination reaction

[reaction: see text]. Alkyne allyl alcohols are readily transformed into beta-amino ethyl alkylidene tetrahydrofurans or beta-amino ethyl alkylidene pyrrolidines in a Pd-catalyzed cycloisomerization-reductive amination sequence with remarkable chemoselectivity leaving benzyl groups and trisubstituted double bonds intact.     

Branched Tertiary Amines from Aldehydes and α-Olefins by Combined Multiphase Tandem Reactions

This study presents the transformation of olefins to branched amines by combining a hydroformylation/aldol condensation tandem reaction with the reductive amination in a combined multiphase system that can be recycled 9 times. The products are branched amines that are precursors for surfactants. Since the multiphase hydrofomylation/aldol condensation system has already been studied, the first step was to develop the partial hydrogenation of unsaturated aldehydes together with a subsequent reductive amination. The rhodium/phosphine catalyst is immobilized in a polar polyethylene phase which separates from the product phase after the reaction. Reaction and catalyst recycling are demonstrated by the conversion of the C₁₄-aldehyde 2-pentylnonenal with the dimethylamine surrogate dimethylammonium dimethylcarbamate to the corresponding tertiary amine with yields up to 88 % and an average rhodium leaching of less than 0.1 % per recycling run. Furthermore, the positive influence of a Bronsted acid and carbon monoxide on the selectivity are discussed. Finally, the two PEG based systems have been merged in one recycling approach, by using the product phase of the hydroformylation aldol condensation reaction for the reductive amination reaction. The yields are stable during a nine recycling runs and the leaching low with 0.09 % over the two recycling stages.     

An efficient synthesis of a new series of acyclonucleosides starting from beta-amino alcohols

A series of new acyclonucleosides analogues 3 has been synthesized very efficiently in three steps starting from beta-amino alcohols 1. The key step of this process is a nucleophilic substitution with various nucleophiles on 2,2'-anhydronucleosides 2. The chemo- and stereoselectivities of this reaction are discussed. AM1 calculations sustained the observed chemoselectivity.     

Metal-free synthesis of aryl esters from carboxylic acids and diaryliodonium salts

An efficient arylation of carboxylic acids with diaryliodonium salts has been developed, giving aryl esters in high yields within short reaction times for both aromatic and aliphatic substrates. The transition-metal-free conditions are compatible with a range of functional groups, and good chemoselectivity is observed with unsymmetric diaryliodonium salts. Furthermore, steric hindrance in the ortho positions is well tolerated both in the carboxylic acid and in the diaryliodonium salt, yielding aryl esters that cannot be obtained via other esterification protocols.     

Characterization of electrospray ionization mass spectrometry for N-diisopropyloxyphosphoryl dipeptide methyl esters

A systematic study of the fragmentation pattern of N-diisopropyloxyphosphoryl (DIPP) dipeptide methyl esters in an electrospray ionization (ESI) tandem mass spectrometry (MS/MS) was presented. A combination of accurate mass measurement and tandem mass spectrometry had been used to characterize the major fragment ions observed in the ESI mass spectrum. It was found that the alkali metal ions acted as a fixed charge site and expelled the DIPP group after transferring a proton to the amide nitrogen. For all the N-phosphoryl dipeptide methyl esters, under the activation of a metal ion, the rearrangement product ion at m/z 163 was observed and confirmed to be the sodium adduct of phosphoric acid mono-isopropyl esters (PAIE), via a specific five-membered penta-co-ordinated phosphorus intermediate. However, no rearrangement ion was observed when a beta-amino acid was at the N-terminal. This could be used to develop a novel method for differentiating isomeric compounds when either alpha- or beta-amino acid are at the N-terminus of peptides. From the [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters (DIPP Xaa1 Xaa2 OMe), the peaks corresponding to the [M+Na Xaa1 C3H6]+ were observed and explained. The [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters with Phe located in the C-terminal, such as DIPPValPheOMe, DIPPLeuPheOMe, DIPPIlePheOMe, DIPPAlaPheOMe and DIPPPhePheOMe, had characteristic fragmentation. Two unusual gas-phase intramolecular rearrangement mechanisms were first proposed for this fragmentation. These rearrangements were not observed in dipeptide methyl ester analogs which did not contain the DIPP at the N-terminal, suggesting that this moiety was critical for the rearrangement.     

Formyl Radical Generation from α-Chloro N-Methoxyphthalimides Enables Selective Aldehyde Synthesis

The aldehydes installation by radical formylation constitutes an attractive synthetic strategy. However, the generation of formyl radicals for organic synthesis applications remains unknown. Herein we report the first formyl radical generation from α-chloro N-methoxyphthalimides, which selectively synthesize aldehydes by alkene hydroformylation under mild photoredox conditions. The aldehydes can be installed on acrylates, acrylamides, vinyl sulfones, vinyl ketones, and complex steroids by radical hydroformylation in excellent chemoselectivity and regioselectivity. The concerted hydrochloride elimination for the formyl radical generation from α-chloro methoxy radicals is established by experimental and computational approaches.     

BCl3‐Mediated Ene Reaction of Sulfur Dioxide and Unfunctionalized Alkenes

The first ene reactions of SO₂ and unfunctionalized alkenes are reported. Calculations suggest that the endergonic ene reactions of SO₂ with alkenes can be used to generate β,γ‐unsaturated sulfinyl and sulfonyl compounds. Indeed, in the presence of one equivalent of BCl₃, the unstable sulfinic acid form stable sulfinic acid?BCl₃ complexes that can be reacted in situ with NCS to generate corresponding sulfonyl chlorides, or with a base to generate corresponding sulfinates. The latter can be reacted with electrophiles to generate sulfones, or with silyl chloride to form β,γ‐unsaturated silyl sulfinates. The sulfinic acid?BCl₃ complexes can be reacted with ethers that act as oxygen nucleophiles to produce corresponding sulfinic esters. Thus one‐pot, three‐component synthesis of β,γ‐unsaturated sulfonamides, sulfinyl esters and sulfones have been developed starting from alkenes and sulfur dioxide (reagent and solvent).     

Catalysis by the Rh/B system Part 1. Vapour-phase hydroformylation of ethylene at atmospheric pressure on Rh/B on silica

A Rh/B system with rhodium crytallites of small dimensions was formed by reducing rhodium trichloride supported on silica with NaBH₄ atlow temperature. Thermal treatments in Ar and/or in CO/H₂ strongly modify the surface composition but induce only a small modification in the crystallite diameter. After treatment in Ar at 543 K and in CO/H₂ the Rh/B system catalyzes the vapor-phase hydroformylation of ethylene at atmospheric pressure in a flow reactor. The reaction proceeds with very good chemoselectivity toward the hydroformylation products (at 398 K, R is ⩾0.7). The formation of the catalytic species and the surface modifications were studied by X-Ray diffraction, FT—IR and XP spectroscopy. The presence of boron seems to play an important role both in preventing sintering of rhodium particles and in favouring good chemoselectivity toward the hydroformylation reaction.     

The first direct enzymatic hydrolysis of alicyclic beta-amino esters: a route to enantiopure cis and trans beta-amino acids

The first direct enzymatic method is reported for the synthesis of cis and trans beta-amino acid enantiomers through the lipase-catalyzed enantioselective hydrolysis of alicyclic beta-amino esters in organic media. High enantioselectivities (E usually >100) were observed when the Candida antarctica lipase B catalyzed reactions were performed with H2O (0.5 equivalents) in iPr2O at 65 degrees C. The resolved products, obtained in good yields (>or=42%), could be easily separated.     

Synthesis of a new chiral bisphospholane ligand for the Rh(I)-catalyzed enantioselective hydrogenation of isomeric beta-acylamido acrylates

The highly stereoselective synthesis of a chiral silylphospholane has been described, which can be advantageously used as a building block under base-free conditions for the construction of diphosphines related to DuPHOS. The utility of silylphospholane is shown in the synthesis of a new bisphospholane ligand 1 (MalPHOS), which is characterized by a maleic anhydride backbone. The ligand forms with Rh(I) a complex with a larger bite angle P-Rh-P than the analogue Me-DuPHOS complex. Both complexes have been tested in the asymmetric hydrogenation of unsaturated alpha- and beta-amino acid precursors of pharmaceutical relevance. In several cases, the new catalyst was superior in comparison to the Me-DuPHOS complex, in particular when (Z)-configured beta-acylamido acrylates were used as substrates.     

一氧化碳参与不饱和烃类化合物羰基化反应的研究进展

不饱和烃类化合物的羰基化反应是指在过渡金属催化剂存在条件下, 将一氧化碳(CO)分子以羰基的形式插入到烯烃(或者炔烃)与不同的亲核试剂中, 合成更高附加值化学品的转化过程. 本文综合评述了羰基化反应合成高附加值化学品的重要性, 介绍了几种不同类型的羰基化反应(氢甲酰化反应、 氢酯化反应、 氢酰胺化反应和氢羧基化反应)在发展新型催化剂体系及高效合成目标产物方面的研究进展, 并对羰基化反应存在的问题及未来发展方向和趋势进行了展望.     

Super long-term highly active and selective hydroformylation in a room temperature-solidifiable guanidinium ionic liquid with a polyether tag

Here we report a novel room temperature-solidifiable guanidinium methanesulfonate with a polyether tag and its use in Rh-catalysed biphasic hydroformylation of higher olefins. This novel ionic liquid can efficiently immobilize the Rh-TPPTS catalyst and render super long-term high activity and chemoselectivity, and no significant loss of activity, selectivity or Rh was observed after thirty-five cycles.     

Dimers of Aleuritic Acid Derivatives

The unsaturated esters of aleuritic acid have been prepared by the condensation method and their oligomerization has been effected by free-radical initiation. The results show that the dimers of unsaturated esters of aleuritic acid were obtained.