Highly efficient nickel/phosphine catalyzed cross-couplings of diarylborinic acids with aryl tosylates and sulfamates

<正>4-Methoxy-4′-methylbiphenyl(3aa) [1] MeO White solid(0.324 g, 82% from aryl tosylate, 0.356 g, 90% from aryl sulfamate); m.p. 111–112 °C; 1H NMR(400 MHz,CDCl3) δ 7.50(d, J = 8.4 Hz, 2H), 7.44(d, J = 8.0 Hz, 2H), 7.21(d, J = 8.0 Hz, 2H), 6.95(d, J = 8.8 Hz, 2H), 3.82(s, 3H), 2.37(s, 3H); 13 C NMR(100 MHz, CDCl3) δ 159.0, 138.0, 136.4, 133.8, 129.5, 128.0, 126.6, 114.2, 55.4, 21.1. 4,4′-Dimethylbiphenyl(3ab) [1] White solid(0.320 g, 88% from aryl tosylate, 0.346 g, 95% from aryl sulfamate); m.p. 122–123 °C; 1H NMR(400 MHz,CDCl3) δ 7.47(d, J = 8.0 Hz, 4H), 7.22(d, J = 8.0 Hz, 4H), 2.37(s, 6H); 13 C NMR(100 MHz, CDCl3) δ 138.4, 136.8, 129.5, 126.9, 21.2.     

Suzuki-Miyaura cross-coupling of alkenyl tosylates with alkenyl MIDA boronates

A practical procedure for the palladium-catalysed Suzuki-Miyaura coupling of various alkenyl tosylates with alkenyl MIDA boronates has been developed. Commercially available trans-bromo[N-succinimidyl-bis(triphenylphosphine)]palladium(II) [Pd(PPh₃)₂NBS] is an effective catalyst under the slow release conditions of MIDA boronates; with less activated alkenyl tosylates addition of the cheap, air-stable tricyclohexylphosphine tetrafluoroborate enhances reactivity.     

Palladium-catalyzed coupling of vinyl tosylates with arylsulfinate salts

The first palladium-catalyzed coupling of vinyl tosylates with arylsulfinate salts is described. A variety of cyclic and acyclic vinyl tosylates were coupled with aryl sulfinate salts using 2.5 mol % Pd₂(dba)₃/5.0 mol % XantPhos to give vinyl aryl sulfone products in good yields. The coupling was extended to the preparation of a cyclopropyl vinyl sulfone.     

An efficient, one-pot synthesis of trithiocarbonates from alcoholic tosylates using the Cs2CO3/CS2 system

A single-step novel protocol for the preparation of symmetrical trithiocarbonates from a corresponding variety of primary, secondary, and tertiary alcoholic tosylates using the Cs₂CO₃/CS₂ system, was developed. This protocol is mild and more efficient than the reported methods.     

A nickel precatalyst for efficient cross-coupling reactions of aryl tosylates with arylboronic acids: vital role of dppf

An air-stable and easy-to-handle nickel precatalyst, (9-phenanthrenyl)Ni(II)(PPh₃)₂Cl, was examined for the cross-coupling reactions of aryl tosylates with arylboronic acids. Under the optimized reaction conditions, the catalytic system tolerates a wide range of activated, neutral and deactivated substrates. The selectivity of this cross-coupling reaction towards aryl tosylates and arylboronic acids has been investigated. It is proposed that ligand 1,1′-bis(diphenylphosphino)ferrocene (dppf) plays a key role in the coupling by enforcing a cis geometry in key intermediates and the active Ni(0) species.     

Norbornanes. Part 20. Inductivity and bridging in 2-norbornyl cations

The solvolysis rates and products of several 1-substituted 2exo- and 2-endo-norbornyl p-toluenesulfonates 7 and 8 , respectively, have been determined. Hydrolyses of these epimeric tosylates yielded rearranged products in varying amounts, except when the substituent was COOCH₃ or CN. The logarithms of the rate constants (log k) for the endo-series 8 correlated linearly with the corresponding inductive constants σ with a reaction constant ρ_I of ?1.24. On the other hand, log k values for the exo-series 7 appear to fit two regression lines, the first line (ρ_I = ?1.90) defined by the tosylates that ionize, with rearrangement, to the tertiary cations 11 , the second (ρ_I = ?1.86) by the tosylates 7 (R = H, COOCH³, and CN) that ionize to an asymmetrically bridged secondary cation 19 . These results confirm the unique participation of C(6) with a ρ_I of ?2.00 in the ionization of 2-exo-nor-bornyl tosylate.     

AN EFFICIENT ONE POT SYNTHESIS OF CARBAMATE ESTERS THROUGH ALCOHOLIC TOSYLATES*

ABSTRACT

An efficient O-alkylation of alcoholic tosylates with amines in a K₂CO₃/CO₂ system in the presence of tetrabutyl ammonium iodide (TBAI) provides exclusive formation of carbamates.

     

Palladium‐Catalyzed Suzuki–Miyaura Cross‐Coupling of Secondary α‐(Trifluoromethyl)benzyl Tosylates

A palladium‐catalyzed C(sp³)−C(sp²) Suzuki–Miyaura cross‐coupling of aryl boronic acids and α‐(trifluoromethyl)benzyl tosylates is reported. A readily available, air‐stable palladium catalyst was employed to access a wide range of functionalized 1,1‐diaryl‐2,2,2‐trifluoroethanes. Enantioenriched α‐(trifluoromethyl)benzyl tosylates were found to undergo cross‐coupling to give the corresponding enantioenriched cross‐coupled products with an overall inversion in configuration. The crucial role of the CF₃ group in promoting this transformation is demonstrated by comparison with non‐fluorinated derivatives.     

Nickel‐Catalyzed Cross‐Electrophile Coupling of Aryl Bromides with Pyrimidin‐2‐yl Tosylates

A new protocol for the NiCl₂ ‐catalyzed cross‐electrophile coupling of aryl bromides with pyrimidin‐2‐yl tosylates to give the corresponding C2 ‐arylation pyrimidine derivatives has been developed. This study provides an improvement over previous methods by using pyrimidin‐2‐yl tosylates instead of halides as coupling partners that are stable and easily available.     

Norbornanes. Part 19. The Inductive Model for Norbornyl Cation Formation

Two CH₃ groups at C(6) of 2-exo- ( 10a ) and 2-endo-norbornyl p-toluenesulfonate 11a lower their solvolysis rates in 80% EtOH by factors of 28 and 16, respectively. A spirocyclopropyl group including C(6), as in 21a and 22a , reduces the rate of exo- and endo-ionization by factors of 250 and 8, respectively. The geminally dimethyl-substituted tosylates 10a and 11a yield the 2-exo-alcohol 10b , whereas the spirocyclopropyl-substituted tosylates 21a and 22a furnish rearranged 3-brendanol 23 . These findings are readily rationalized by the inductive model, according to which norbornyl cation formation is controlled by the inductive effect of dorsal substituents.     

An efficient,one-pot synthesis of trithiocarbonates from alcoholic tosylates using the Cs<Subscript>2</Subscript>CO<Subscript>3</Subscript>/CS<Subscript>2</Subscript> system

A single-step novel protocol for the preparation of symmetrical trithiocarbonates from a corresponding variety of primary, secondary, and tertiary alcoholic tosylates using the Cs₂CO₃/CS₂ system, was developed. This protocol is mild and more efficient than the reported methods. Correspondence: Devdutt Chaturvedi, Bio-Organic Chemistry Division, Indian Institute of Integrative Medicine, Canal Road, Jammu-Tawi-18000, J&K, India.     

Synthesis of Polyfluorinated Ethers

Procedures for preparing polyfluorinated ethers H(CF₂CF₂) _n CH₂OR by alkylation of the corresponding telomeric alcohols H(CF₂CF₂) _n CH₂OH (n = 1–3) with alkyl halides and alkyl tosylates were examined.     

Cyclocarbonylation of unsaturated tosylates as a method of cyclanone synthesis

A study has been made to determine the scope of the cyclocarbonylation reaction of olefinic tosylates with Na₂Fe(CO)₄.     

Side-chain reactions in π-chromium tricarbonyl-complexed arenes IV. Solvent and deuterium isotope effects in E2 reactions of some 2-phenylethyl and 1-phenyl-2-propyl derivatives

The rates and products of elimination with sodium ethoxide in ethanol, and potassium t-butoxide in t-butanol, of chromium tricarbonyl-complexed (2-phenylethyl bromides), (2-phenylethyl tosylates), (1-phenyl-2-propyl bromides), and (1-phenyl-2-propyl tosylates) were determined. Complexation increases the rate of elimination, the size of the effect depending on leaving group, solvent/base system and, to a minor extent structure. The Cr(CO)₃ group increases the olefin percentage when substitution competes with elimination, whereas the relative proportions of the olefin isomers obtained from secondary substrates are practically unchanged whether the ring is complexed or not. Deuterium isotope effects have been measured for the elimination from uncomplexed, complexed and 2-(p-nitrophenyl)ethyl compounds. The magnitude of the isotope effect does not vary appreciably with substituents.     

Rh(I)-catalyzed cross-coupling reactions of alkenyl tosylates with potassium aryltrifluoroborates

RhCl(PPh₃)₃/DPPF was successfully employed as an efficient catalyst in the Suzuki-Miyaura cross-coupling reactions of potassium aryltrifluoroborates with alkenyl tosylates, affording the corresponding products in good to excellent yields.     

Iron‐catalyzed cross‐coupling of heteroaromatic tosylates with alkyl and aryl Grignard reagents

An Fe(III)‐catalyzed cross‐coupling of N‐heteroaromatic tosylates with aryl and alkyl Grignard reagents is presented. The reaction proceeds at ?20°C to room temperature with short reaction time (15–30 min.), and the corresponding products are obtained with moderate to high yields. In particular, low‐cost and abundantly available FeCl₃ or Fe(acetylacetonate)₃ catalyze the reaction without other special ligands. All tested N‐heteroaromatic tosylates that are available including pyridine and pyrimidine derivatives were subject to the reaction, resulting in the expected products. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthèse de fluoro-2 monoalkylhydrazines

Substitution reactions of the tosyl group in 2-fluorotosylates seem to be easier than in homologous non-fluorinated tosylates [1,2]. Accordingly, the reaction of NH₂NH₂ on these 2-fluorotosylates was investigated, and hitherto unknown 2-fluoromonoalkylhydrazines were obtained in acceptable yields.     

High-yield catalytic metathesis of alkenyl tosylates with applications in organic synthesis

Alkenyl tosylates of the type RCHCH(CH₂)_nOTs [RH, n=9; RH, n=7; and RCH₃(CH₂)₇, n=8] undergo metathesis using a WCl₆-Me₃SnCl catalyst system, producing difunctionalised alkenes of the type TsO(CH₂)_nCHCH(CH₂)_nOTs (n=7,8, and 9); examples of the use of these products in synthesis are presented.     

Chemoselective reduction of β-butyltellanyl α,β-unsaturated carbonyl compounds to allylic alcohols

(Z)-β-Butyltellanyl α,β-unsaturated carbonyl compounds were stereoselectively produced by hydrotelluration of alkynones or by an addition/elimination sequence from enol tosylates. The β-butyltellanyl-enones were chemoselectively reduced with NaBH₄/MeOH, NaBH₄·CeCl₃·7H₂O/MeOH and DIBAL-H systems to the corresponding allylic alcohols with retention of the Z stereochemistry.     

Nickel‐catalyzed Buchwald–Hartwig amination of pyrimidin‐2‐yl tosylates with indole,benzimidazole and 1,2,4‐triazole

Nickel‐catalyzed Buchwald–Hartwig amination of pyrimidin‐2‐yl tosylates with indole and benzimidazole was achieved using Ni(dppp)Cl₂ as catalyst, yielding a variety of novel C2‐substituted pyrimidine derivatives in good yields. This reaction proved to be tolerant of various pyrimidin‐2‐yl tosylates bearing either electron‐donating or electron‐withdrawing groups as well as nucleophiles including indole, benzimidazole and 1,2,4‐triazole. Copyright © 2016 John Wiley & Sons, Ltd.