Synthesis and N-C bond cleavage reactions for cyclic phosphazenium dications.

Phosphazenium cations were first characterized 60 years ago and yet little is known of their reactivity. The bidentate phosphonium dicationic salts [(CH)(PPhF)][B(CF)]2 and [(CH)(PPhCl)][Cl]3 were prepared. Reaction of 2 with (MeSi)NMe gave the phosphazenium dication [(CH)(PPh)(μ-NMe)][B(CF)]4, while reaction of 3 with two equivalents of MeN(SiMe) gave the related dication [(CH)(PPhNMe)][Cl]5.

Reactions of 1,1- and 1,2-bis-boranes with a protic diamine and hydrazine.

The reactions of 1,1- and 1,2-bis-boranes, PhCHCH(B(CF))1 and MeSiCH(B(CF))CHB(CF)2, with -phenylenediamine and hydrazine are reported. The coordination of -phenylenediamine gives the expected adducts, PhCHCH(B(CF)(HN))CH4 and MeSiCH(B(CF))CHB(CF)((HN)CH) 6. Under thermal duress, 4 undergoes retrohydroboration, resulting in the reaction of the diamine with HB(CF) to give (CF)B(NH)(NH)CH5.

Reactivity of -(isocyanoimino)triphenylphosphorane toward group 13 Lewis acids.

The species PhPNNC 1 reacts with the group 13 Lewis acids E(CF) (E = B or Al), HB(CF), ClAl(CF) and ECl (E = Ga or In) to give the Lewis acid-base adduct PhPNNCB(CF) 2, the zwitterionic product (PhPNH)B(CF)CNB(CF)H 3, the chelated salts [(PhPNNC(CN)NPPh)ER][EXR] (E = Al, R = X = CF, 4; E = Al, R = CF, X = Cl, 5; E = Ga, R = X = Cl, 6), and the neutral species [(PhPNNC(CN)NPPh)InCl] 7. The nature of these variations in reactivity are rationalized and the potential utility considered.

Correction: A chelated borinium cation.

Correction for 'A chelated borinium cation' by Christopher Major , , 2024, , 10075-10078, https://doi.org/10.1039/D4DT01242A.

A chelated borinium cation.

Two coordinate boron cations are rare. Herein we report the synthesis of [RNSiMeCH]BF (R = Dipp 3, 1-Ad 5) (Dipp = CH(iPr), Ad = CH) the reaction of BF with the corresponding dilithiated diamides. Subsequent abstraction of fluoride provided the corresponding borinium salts, [(RNSiMeCH)B][B(CF)] (R = Dipp 6, 1-Ad 8).

Fluorination/Dearomatization of CF Groups: An FLP Route to an Electrophilic Borane and Non-Coordinating Anions.

B(CF) and the corresponding anion [B(CF)] are ubiquitous in main group and transition metal chemistry. Known derivatives are generally limited to the incorporation of electron donating substituents. Herein we describe electrophilic fluorination and dearomatization of such species using XeF in the presence of BF or Lewis acidic cations.

Synthesis and Reactivity of the [NCCCO] Cyanoketenate Anion.

Cyanoketene is a fundamental molecule that is actively being searched for in the interstellar medium. Its deprotonated form (cyanoketenate) is a heterocumulene that is isoelectronic to carbon suboxide whose structure has been the subject of debate. However, the investigation of cyanoketene and its derivatives is hampered by the lack of practical synthetic routes to these compounds.

Triple -substitution reactions of B(CF) and [(CF)PF] with P(SiMe).

-Substitution reactions on CF rings of Lewis acids have been exploited to achieve triply substituted derivatives. The reaction of B(CF) with P(SiMe) ultimately affords the Lewis acid B(CFP(SiMe))1. This species binds Lewis bases affording the adducts LB(CFP(SiMe)) (L = MeCN 2, OPEt3, PMe4, PBu5) and reacts with LiMe to give the salt [Li][MeB(CFP(SiMe))]·3THF 6.

Boron diamide derivatives containing N-N and N-P molecular fragments.

The cationic and neutral boron-diamide precursors are employed to target the inclusion of N and N-P molecular fragments. The species (HCN(Dipp))BNH5, and (HCN(Dipp))BNH6 were prepared. While efforts to oxidize with [NO] gave mixtures of products, reactions with NH gave the salts [(HCN(Dipp))B(NHNH)][OSCF] 7 [(HCN(Dipp))B(NHNH)][OSCF] 8.

Addition and NN bond cleavage of diazo-compounds by phosphino-phosphenium cations.

The phosphino-phosphenium cation (PPC) [PhPPPh][GaCl] reacts as a frustrated Lewis pair to add across the NN bond of (BuOCN). In contrast, photolytical addition [PhClPPPh][GaCl] to (RN) results in cleavage of the NN bond affording [PhP(μ-NR)PPhCl][GaCl] (R = Ph 2, CHCl). While the chloride of 2 is replaced with N or CN reaction with MeSiN or BuNC respectively, reaction with (CF)BH effects ring opening to give [HN(Ph)PPh(μ-NPh)PPh][GaCl] 7.

The Lewis superacidic aluminium cation: [(NHC)Al(CF)].

The aluminium salt [(NHC)Al(tol)(CF)][B(CF)], (NHC = CH(N(iPrCH))) is shown to behave as a Lewis superacid as it abstracts fluoride from [SbF]. It also acts as a Lewis acid catalyst for hydrosilyation, hydrodefluorination and Friedel-Crafts reactions.

Coordination chemistry and FLP reactivity of 1,1- and 1,2-bis-boranes.

Coordination chemistry and frustrated Lewis pair (FLP) chemistry have been most commonly studied using monodentate Lewis acids. In this paper, we examine the corresponding reactions employing the 1,1- and 1,2-bis-boranes, PhCHCH(B(CF))1 and MeSiCH(B(CF))CHB(CF)2, respectively. Coordination of isocyanide to these species results in the formation of the products RCH(B(CF)CNBu)CH(B(CF)CNBu) (R = Ph 3, MeSi 4).

The impact of Lewis acid variation on reactions with di--butyl diazo diesters.

Reactions of (BuOCN) with Lewis acids and FLPs have previously been shown to prompt the formation of diazene compounds. In this work, we show that the reaction of (BuOCN) with 9-BBN leads to a bicyclic heterocyclic product (BuOCO(BBN)CN)1. In contrast, the reactions of (BuOCN) with BF or [EtSi][B(CF)] lead to the isolation of [BuNHNHBu][BF] 2 and [BuN(H)NBu][B(CF)] 3, respectively.

Borane catalyzed transesterification of -butyl esters using α-aryl α-diazoesters.

The B(CF)-catalyzed transesterification of a series of 3-alkenyl-oxindoles and other unsaturated -butyl esters with aryl-diazo esters is reported. This protocol is facile and generally high yielding proceeding under mild conditions and is remarkably chemoselective leaving the CC bonds intact.

B(CF)-catalyzed hydrogermylation of enones: a facile route to germacycles.

Organogermacycles are important skeletons for medicinal chemistry and materials. Herein, we reported a B(CF) mediated domino hydrogermylation reaction of enones with dihydrogermanes, affording 21 variants of organogermacycle compounds. These germacyclic compounds were obtained in good to excellent yields (up to 99% yield) under mild reaction conditions.

Correction: Stannyl phosphaketene as a synthon for phosphorus analogues of β-lactams.

Correction for 'Stannyl phosphaketene as a synthon for phosphorus analogues of β-lactams' by Yong-an Luo , , 2023, https://doi.org/10.1039/d3cc03117a.

Phosphino-Phosphination Reactions: Frustrated Lewis Pair Reactivity of Phosphino-Phosphonium Cations with Alkynes.

The phosphino-phosphonium cations of the form [R PPR' ] are labile and provide access to the constituent Lewis acidic and Lewis basic fragments. This permits frustrated Lewis pair-type addition reactions to alkynes, affording unprecedented phosphino-phosphination reactions and giving cations of the form [cis-R PCHC(R'')PR' ] . This reactivity is further adapted to prepare several examples of a rare class of dissymmetric cis-olefin-linked bidentate phosphines.

Stannyl phosphaketene as a synthon for phosphorus analogues of β-lactams.

The reaction of the stannyl phosphaketene (Nacnac)SnPCO 1 (Nacnac = CH{(CMe)(2,6-PrCHN)}) with B(CF) produced the 1,4-addition product of (Nacnac)SnPCO(B(CF)). However, the corresponding reactions in the presence of dimethyl maleate, diisopropyl fumarate or diethyl-but-2-ynedioate gave [2+2] addition yielding four-membered phosphacycles, ((Nacnac)Sn(MeOC))CHPC(OB(CF))CH(COMe), [(CF)B)PC(OSn)C(COMe)CH(COMe)], (Nacnac)Sn(PrOC)CC(OAl(CF))P[CH(COPr)CH(COPr)]CH(COPr), and (Nacnac)SnP (EtOCCC(COEt))CO(B(CF)), respectively. In contrast, the corresponding reaction of phenylacetylene gave the FLP-addition product (Nacnac)SnOC(P)C(Ph)CH(B(CF)).

Electron-deficient cyclopropenium cations as Lewis acids in FLP chemistry.

Cyclopropenium cations incorporating electron deficient substituents are Lewis acidic despite the presence of π-electrons. The chloride and electron affinities are examined computationally and experimentally, respectively. These cations form classic Lewis acid-base adducts with PPh, while sterically demanding phosphines yield frustrated Lewis pairs (FLPs) which participate in FLP additions.

Frustrated Lewis pair chemistry of CO.

Transition metal species readily capture and react with CO as the metal can act both as an acceptor and donor of electron density. In contrast, such a situation is less common in the main group and thus far fewer examples of main group CO adducts and their subsequent reactivity have been studied. In this review, we focus on the application of the concept of Frustrated Lewis Pairs (FLPs) to develop main group chemistry of CO.

Reactivity of frustrated Lewis pairs with BOC protected diazocarboxylates: FLP capture of diazene.

Reactions of (BuOCN) with FLPs are examined. B(CF) interacts with the carbonyl oxygen atoms inducing loss of CHCMe; however, in the presence of basic donors, the protons are intercepted affording the salts [Hbase] [((CF)BOCN)] (base = BuP 1, NCHPh2, HNCHMe3). In contrast, in the presence of (-Tol)P, a proton transfers to the diazo-N atom affording (-Tol)PN(COBu)NHB(CF)4.

Reactive FLP-alkyne addition products: a route to anionic and zwitterionic phosphines.

Combination of a phosphinidene precursor, B(CF) and 4-ethynyltoluene afforded the FLP addition product, EtN(CH)PC(Tol)CH (B(CF)) 2. Compound 2 reacted with halides, pseudo-halides or MeSiSPh to provide a facile route to the salts of anionic phosphines while reaction with PEt gave the zwitterion EtPCHC(SiMe)P(NEt)C(Tol)CHB(CF)8. This latter species reacted with an alkyne to give a phosphine donor with both olefin-linked cationic and anionic substituents.

Diazene Chemistry: Metal-Free Models of N Reduction Intermediates.

Interest in main group chemistry related to the Haber-Bosch process has drawn less attention than that of transition metal species. Herein, we show that the steric demands in (BuOCN) block initial interaction of B(CF) with nitrogen and prompt loss of methylpropene and CO to diazene (NH) borane adduct and the analogous hydrazine (NH) adduct . These species react with basic phosphines to give anions of and containing NH and NH fragments, respectively.

B(CF)-catalyzed cyclopropanation of 3-alkenyl-oxindoles with diazomethanes.

Spirocyclopropane-oxindoles are key motifs in biologically active compounds and are versatile synthetic intermediates. Herein, we report a metal-free, B(CF) catalyzed cyclopropanation of 3-alkenyl-oxindoles with diazomethanes. This provides 25 variants of spirocyclopropane-oxindole derivatives.

Alkoxyphosphorane/Borane Cooperative Alkylations: A Frustrated Lewis Pair Version of the Mitsunobu Reaction.

The combination of the alkoxyphosphoranes, Ph P(OR)(O C Cl ) and the borane B(C F ) generates the zwitterions 3 which act as FLP to effect the alkylation of several nucleophiles affording C-C, C-N, C-H and C-Cl coupling products. A DFT study shows the reaction proceeds via an FLP activation pathway generating an alkoxyphosphonium intermediate which effects the alkylation of the nucleophiles, akin to the Mitsunobu reaction.