Mechanism of Phosphine‐Catalyzed Allene Coupling Reactions: Advances in Theoretical Investigations

Organocatalysis has emerged as an effective strategy for chemical synthesis. Within this area, phosphine‐catalyzed coupling reactions have attracted considerable attention because of their versatility and wide range of applications in the construction of new C?C bonds. Recently, various experimental studies on the phosphine‐catalyzed coupling reaction of allenes have been reported, and mechanistic and computational studies have also progressed considerably. As a nucleophile, phosphine can react with an allene to form a zwitterionic phosphoniopropenide intermediate. After stepwise cycloaddition and proton transfer, the phosphine catalyst can be regenerated by C?P bond cleavage. Alternatively, the zwitterionic phosphoniopropenide intermediate could also be protonated by a Brønsted acid to generate a phosphonium intermediate, which can be used to construct new C?C bonds by electrophilic addition. In this review, we have summarized details of mechanistic studies of phosphine‐catalyzed allene coupling reactions that follow these two reaction modes. In addition to detailing the reaction pathway, the regioselectivity and diastereoselectivity of the phosphine‐catalyzed allene coupling reaction are also discussed in this review.     

Tuning Catalysts to Tune the Products: Phosphine‐Catalyzed Aza‐Michael Addition Reaction of Hydrazones with Allenoates

A new tunable phosphine‐catalyzed aza‐Michael β‐addition reaction between allenoates and various hydrazones has been developed. These reactions are most‐efficiently promoted by a catalytic amount of phosphine catalysts. These atom‐economical reactions are operationally simple and their corresponding adducts can been achieved in high yields and high selectivity under mild reaction conditions. Further studies revealed that different phosphine catalyst can produce different adducts from the same starting materials.     

Intramolecular arene epoxidation by phosphadioxiranes

Singlet oxygen reacts with binaphthyl phosphine derivatives such as 1,1'-binaphthyl di-tert-butyl phosphine to form the corresponding binaphthyl-2-oxide phosphine oxides. This new intramolecular arene epoxidation reaction proceeds with complete retention of stereochemistry. The binaphthyl-2-oxide di-tert-butyl phosphine oxide undergoes a slow "NIH-rearrangement" to form the corresponding hydroxylated product. A transient phosphadioxirane intermediate has been directly observed by low-temperature NMR. Kinetic analyses show that all of the phosphadioxirane intermediate is converted to product. [reaction: see text]     

Ruthenium‐Catalyzed ortho C−H Borylation of Arylphosphines

Efficient, phosphine‐directed ortho C?H borylation of arylphosphine derivatives was achieved using Ru catalysts for the first time. The reaction is applicable to various tertiary arylphosphine and arylphosphinite derivatives to give (o‐borylaryl)phosphorus compounds in high yields. This reaction enables easy access to a variety of functionalized phosphine ligands and ambiphilic phosphine boronate compounds, thus realizing a new late‐stage modification of phosphorus compounds.     

Organische Phosphorverbindungen XXV Darstellung und Eigenschaften von sekundären und tertiären Phosphinsulfiden

Two new processes for the preparation of sec. phosphine sulfides which involve reaction of dialkylamino-dialkyl or diaryl phosphines with hydrogen sulfide, and of dialkylthionophosphonates, (RO)₂P(S)H, with GRIGNARD or organolithium reagents, respectively, are described. The addition of sec. phosphine sulfides to olefins and the condensation of sec. phosphine sulfides with N-hydroxymethyldialkylamines are reported. The conversion of tert. Phosphine sulfides to the corresponding tert. phosphine oxides is readily achieved with hydrogen peroxyde. The physical properties of several new unsymmetrical tert. phosphine sulfide and oxides are listed.     

醚功能化的膦配体的合成、负载及其在钯催化的Suzuki-Miyaura反应中的应用

合成了一种新的醚功能化的二茂铁膦3,连到Merrifield树脂上形成负载型的膦配体4;分别开展了膦配体3及其负载型的4在钯催化的Suzuki-Miyaura偶联反应中催化研究;发现相应形成的均相和多相钯催化剂可高产率地催化一系列的溴代芳烃与芳基硼酸偶联形成相应的联芳烃,以及负载型催化剂在不补加钯时具有一定的循环性能.     

Markovnikov hydroformylation catalyzed by ROPAC in the presence of phosphine and phosphine oxide ligands

Rhodium-catalyzed hydroformylation of 1-octene in the presence of different phosphine and phosphine oxide ligands has been investigated. The molecular structure of new phosphine ligand, fluorenylidine methyl phenyl diphenylphosphine, was determined by single-crystal X-ray crystallography. Parameters such as different ligands, molar ratio of ligand to rhodium complex, ratio of olefin to rhodium complex, pressure of CO : H₂ mixture, and time of the reaction were studied. The linear aldehyde was the main product when the phosphine ligands were used as auxiliary ligands while the selectivity was changed to the branched products when the related phosphine oxide ligands were used. Under optimized reaction conditions, in the presence of [Rh(acac)(CO)(Ph₃P)]-di(1-naphthyl)phenyl phosphine oxide, conversion of 1-octene reached 97% with 87% selectivity of branched aldehyde.     

Synthesis and characterisation of a new helically chiral ruthenium complex

A new helically chiral hexacyclic phosphine, containing one thiophene ring was prepared in good yield via a five-step sequence involving a palladium-catalysed Mizoroki-Heck coupling reaction and classical oxidative photocyclisation. A mononuclear air stable ruthenium complex of this phosphine was also prepared and characterised.     

Photo‐promoted Skeletal Rearrangement of Phosphine–Borane Frustrated Lewis Pairs Involving Cleavage of Unstrained C−C σ‐Bonds

An unprecedented photo‐promoted skeletal rearrangement reaction of phosphine–borane frustrated Lewis pairs, o‐(borylaryl)phosphines, involving cleavage of an unstrained sp²C–sp³C σ‐bond is reported. The reaction realizes an efficient synthesis of cyclic phosphonium borate compounds. The reaction mechanism via a boranorcaradiene intermediate is proposed based on theoretical calculations. This work sheds light on the new photoreactivity of phosphine–borane FLPs.     

葡萄糖衍生物的手性膦化合物的合成及结构研究

研究葡萄糖吡喃环上同时含有官能团环氧乙烷基和对甲苯磺酸酯时与二苯基膦锂的反应, 一种新的手性膦被得到。它的膦氧化物的晶体结构被测定, 构象为椅式(1C4), 吡喃环上的五个取代基均在直立键上。     

Photo-promoted Skeletal Rearrangement of Phosphine–Borane Frustrated Lewis Pairs Involving Cleavage of Unstrained C−C σ-Bonds

An unprecedented photo-promoted skeletal rearrangement reaction of phosphine–borane frustrated Lewis pairs, o-(borylaryl)phosphines, involving cleavage of an unstrained sp²C–sp³C σ-bond is reported. The reaction realizes an efficient synthesis of cyclic phosphonium borate compounds. The reaction mechanism via a boranorcaradiene intermediate is proposed based on theoretical calculations. This work sheds light on the new photoreactivity of phosphine–borane FLPs.     

Synthesis of New Phosphines and P-Heterocycles from Phosphonates Containing Allyl Group

Addition of phenylphosphine to allylphosphonate followed by reduction of the resulting diphosphonate gives a new branched phosphine, bis(3-phosphinopropyl)phenylphosphine. Its reaction with paraform and p-toluidine yields oligomeric 3-[3-(propylenophenylphosphino)propyl]-1,5-di-p-tolyl-1,5,3,7-diazadiphosphacyclooctane. Diethyl (5-allyl-2-ethoxybenzyl)phosphonate was obtained. Its reduction gives unsaturated (5-allyl-2-ethoxybenzyl)phosphine. This product adds two moles of formaldehyde to give bis(hydroxymethyl)(5-allyl-2-ethoxybenzyl)phosphine. The reaction of this compound with p-toluidine yielded, depending on the conditions, the corresponding bis(aminomethyl)phosphine, 1,3,5-diazaphosphorinane, and 1,5,3,7-diazadiphosphacyclooctane, and also their derivatives containing allyl substituents.     

新型膦酰基取代的脂环化合物的合成研究及手性拆分

研究了二(二苯基氧化膦)乙炔同取代环戊二烯的Diels-Alder反应，合成了四个新型有机膦脂环化合物，并用^1H NMR，MS和元素分析确定了它们的结构，同时以(±)-二苯甲酰酒石酸为拆分剂，对外消旋9,10-二氢-9,10-亚乙烯基-2,3-苯并蒽-11,12-二(二苯基氧化膦)进行了拆分，得到了两个有光学活性的产物。     

Intramolecular Phosphine-Promoted Knoevenagel Based Redox-Reaction

A Knoevenagel based redox-reaction promoted by intramolecular phosphine sources is presented for the first time. The influence of different diketones, aldehydes, bases and acids was investigated. The effects of different substituents were evaluated based on their electronical influence on the diketone structure. With the obtained results a mechanism is proposed, giving information about transition states formed during the reaction, which can lead to different products. This type of an internal redox transformation with a phosphine oxide moiety remaining in the molecule after the redox reaction represents a new type of reaction.     

Phosphorus(V)-catalyzed deoxydichlorination reactions of aldehydes

A phosphine oxide-catalyzed conversion of aldehydes into 1,1-dichlorides is reported. The reaction proceeds via a phosphorus(V)-catalysis manifold in which phosphine oxide turnover is achieved using oxalyl chloride as a consumable reagent. The new method is applicable to a range of aldehydes and, in combination with palladium-catalyzed reductive dimerization, gives rise to a new catalytic approach to the synthesis of stilbenes and a short formal synthesis of resveratrol.     

Neutral nickel oligo- and polymerization catalysts: the importance of alkyl phosphine intermediates in chain termination

An unconventional chain termination reaction has been explored for the SHOP (Shell higher olefin process)-type, anilinotropone, and salicylaldiminato nickel-based oligo- and polymerization catalysts by using density functional theory (DFT). Starting from the tetracoordinate alkyl phosphine complex, the termination reaction was found to involve a rearrangement of the alkyl chain to form a pentacoordinate β-agostic complex, β-hydride elimination, and olefinic chain dissociation and to compete with propagation at sufficiently high phosphine concentration and/or basicity. It provides the first complete and convincing mechanistic rationale for the decreasing chain lengths observed upon increasing phosphine concentration and basicity. The unconventional reaction was found to be a major termination pathway for the SHOP-type catalyst and is very unlikely to lead to branching and olefin isomerization, which is critical for explaining why the SHOP catalyst, in contrast to the anilinotropone and salicylaldiminato catalysts, tends to lead to the oligomerization of ethylene to form linear α-olefins. Based on our results we have proposed a new and extended catalytic cycle for the SHOP-type ethylene oligomerization catalyst. Finally, the importance of the new termination reaction for the SHOP-type catalyst suggests that this reaction may also operate with other ethylene oligomerization nickel catalysts. This prediction was confirmed for a pyrazolonatophosphine catalyst, for which the new termination route was found to be even more facile, which explains the short oligomers produced by this catalyst.     

Catalytic phosphorus(V)-mediated nucleophilic substitution reactions: development of a catalytic Appel reaction

Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.     

Systematic survey of positive chlorine sources in the asymmetric Appel reaction: oxalyl chloride as a new phosphine activator

A wide selection of phosphine activators has been screened to improve the selection process in the asymmetric Appel reaction. Of the activators screened, hexachloroacetone (HCA) gave the highest selectivity with excellent yield, but at least one of its by-products, pentachloroacetone (PCA), can become involved in the selection process. In addressing this, a new reaction of phosphines with oxalyl chloride was discovered that can also generate the key intermediate chlorophosphonium salt (CPS), gives better enantioselectivity and possesses significant advantages over other phosphine activators.     

In situ phosphine oxide reduction: a catalytic Appel reaction

Several important reactions in organic chemistry thrive on stoichiometric formation of phosphine oxides from phosphines. To avoid the resulting burden of waste and purification, cyclic phosphine oxides were evaluated for new catalytic reactions based on in situ regeneration. First, the ease of silane-mediated reduction of a range of cyclic phosphine oxides was explored. In addition, the compatibility of silanes with electrophilic halogen donors was determined for application in a catalytic Appel reaction based on in situ reduction of dibenzophosphole oxide. Under optimized conditions, alcohols were effectively converted to bromides or chlorides, thereby showing the relevance of new catalyst development and paving the way for broader application of organophosphorus catalysis by in situ reduction protocols.     

Asymmetric catalytic aza-Morita-Baylis-Hillman reaction using chiral bifunctional phosphine amides as catalysts

The asymmetric catalytic aza-Morita-Baylis-Hillman reaction of N-sulfonated imines with α,β-unsaturated ketones has been successfully conducted by using chiral bifunctional phosphine amides as catalysts. A series of new chiral bifunctional phosphine amides were designed, synthesized, and systematically studied for this asymmetric reaction. The corresponding aza-MBH adducts were obtained in good yields (75-99%) and up to very good enantiomeric excesses (51-95% ee) under mild conditions.