Pyridinium N-2′-pyridylaminide: synthesis of 3-aryl-2-aminopyridines through an intramolecular radical process

Tris(trimethylsilyl)silane (TTMSS) and azobisisobutironitrile (AIBN) promote the intramolecular heteroarylation of arenesulfonamides with pyridyl radicals under thermal conditions. The arenesulfonamides are easily prepared from pyridinium N-2′-pyridylaminide. The heteroarylation process involves pyridyl radical cyclization and ipso substitution.     

Synthesis of biaryls via intermolecular radical addition of heteroaryl and aryl bromides onto arenes

Tris(trimethylsilyl)silane (TTMSS) and azobisisobutironitrile (AIBN) promoted the easy intermolecular arylation of aryl and heteroaryl bromides under thermal conditions via a radical pathway.     

Synthesis of benzocycloalkene derivatives via Pd-catalyzed one-pot two-step reactions of benzocyclic ketones,tosylhydrazide with aryl bromides

A new method for the synthesis of benzocycloalkene derivatives is described, through the palladium-catalyzed one-pot two-step reactions of benzocyclic ketones, tosylhydrazide with aryl bromides. Palladium-carbene complex as an important intermediate undergoes migratory insertion to form benzylpalladium complex, followed by a fast β-hydride elimination to give substituted benzocycloalkenes. The advantages of this reaction include readily available starting materials, broad substrate scope, high efficiency, and gram scale synthesis.     

Gold(I)-catalyzed direct C-H arylation of pyrazine and pyridine with aryl bromides

An efficient procedure for the direct C-H arylation of electron-poor aromatics such as pyrazine and pyridine with aryl bomides is described. In the presence of catalytic amount of Cy₃PAuCl and with the use of t-BuOK as base, pyrazine undergoes the direct C-H arylation with aryl bromides at 100 °C, and the yields of the arylated products depend on the nature of aryl bromides. In the cases of electron-rich aryl bromides used, the arylated pyrazines can be obtained in good to high yields. For electron-poor aryl bromides, the addition of AgBF₄ is the crucial point to accelerate the coupling reaction to give the arylated products in moderate yields. Pyridine also reacts with electron-rich aryl bromides catalyzed by Cy₃PAuCl to give a mixture of arylated regioisomers in moderate yield. However, in order to realize the direct C-H arylation of pyridine with electron-poor aryl bromides, the addition of silver salt as additive and a milder reaction temperature (60 °C) are required.     

The reaction of benzothiazole sulfenamide with (TMS)3SiH: An example of degenerate-branched chain process

The reaction of sulfenamide 3 with (TMS)₃SiH initiated by the decomposition of AIBN at 76 °C has been studied in some detail. The reaction is a rare example of a radical chain-branching process. The two main products are dialkylamine 4 and the thiosilane 5. It is also established that 2-mercaptobenzothiazole (2) is formed in a substantial yield as one of the by-products. The mechanism of this chain autocatalytic reaction is complex due to a mix of different radical chain reactions and some discussion is provided. The amine obtained in a quantitative yield can arise from two independent routes of attack of (TMS)₃Si radical on sulfenamide 3. The minor route affords thiol 2 that can act as a catalyst for the major route during the reaction course and then gives a salt with secondary amine, which precipitates upon cooling. The origin of autocatalysis is discussed in some detail.     

Reaction of aryl azides with tris(trimethylsilyl)silyllithium: Synthesis of tmeda or thf adducts of [Li{N(Ar)Si(SiMe3)3}] and 1,4-trimethylsilyl migration from oxygen to nitrogen

Reaction of ArN₃ (Ar = Ph, p-MeC₆H₄, 1-naphthyl) with [Li{Si(SiMe₃)₃}(thf)₃] yielded lithium amides [Li{N(Ar)Si(SiMe₃)₃}L] (L = tmeda or (thf)₂). Similar treatment of o-phenylene diazide with 2 equiv. of [Li{Si(SiMe₃)₃}(thf)₃] formed dilithium diamide complex 4. Reaction between o-Me₃SiOC₆H₄N₃ and [Li{Si(SiMe₃)₃}(thf)₃] afforded, via 1,4-trimethylsilyl migration from oxygen to nitrogen, [Li{OC₆H₄{N(SiMe₃)Si(SiMe₃)₃}-2}]₂ (5). The structures of complexes 3 and 5 have been determined by single crystal X-ray diffraction techniques.     

Room temperature Pd(0)/Ad3P-catalyzed coupling reactions of aryl chlorides with bis(pinacolato)diboron

Room temperature Pd(0)/Ad₃P-catalyzed cross-coupling reactions of aryl chlorides with bis(pinacolato)diboron are described. The Pd(0)/Ad₃P catalyst, generated from Ad₃P-coordinated acetanilide-based palladacycle complex, proved to be an efficient catalyst system for the Miyaura borylation reactions of a variety of aryl chlorides with bis(pinacolato)diboron. The mild reaction condition, the easy availability of the catalyst and good coupling yields make these reactions potentially useful in organic synthesis.     

Synthesis of diphenyl[alkyl(aryl)trimethylsiioxymethyl]phosphines

A series of previously unknown diphenyl[alkyl(aryl)trimethylsiloxymethyl]phosphines was prepared by the reaction of diphenyl(trimethylsilyl)phosphine with carbonyl compounds. The first complexes of these ligands with palladium chloride were prepared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 754–756, April, 1994.     

Free radical reactions for heterocycle synthesis. Part 7: 2-Bromobenzoic acids as building blocks in the construction of spirobenzolactones and spirobenzolactams

A straightforward 2-step parallel synthesis for structurally diversified spiro compounds is developed. 2-Bromobenzoic acids are used as common building blocks to couple with a series of conjugated enoles or enamines. Sequential intramolecular free radical Michael additions lead to formation of spirobenzolactones, spirobenzolactams, spirobenzolactone-lactams, spiorbenzolactone-thiolactones, spiordilactones, and bridged-spirolactones.     

Oxidative cross-coupling of allyl(trimethyl)silanes with aryl boronic acids by palladium catalysis

The first oxidative cross-coupling of allylsilanes with aryl boronic acids has been developed by palladium catalysis. The reaction between β-substituted allyl(trimethyl)silanes and a wide range of aryl boronic acids afforded allylarenes in moderate to good yields and excellent selectivity. On the basis of experimental results and literature reports, it was suggested that the reaction might start from transmetalation of aryl boronic acid with AgOAc followed by transmetalation with Pd(II) to give an arylpalladium acetate complex as a key intermediate. This intermediate underwent either electrophilic addition/desilylation or transmetalation with allylsilane and subsequent reductive elimination to give the final product.     

Synthesis of diblock copolymers by combining stable free radical polymerization and atom transfer radical polymerization

A stable nitroxyl radical functionalized with an initiating group for atom transfer radical polymerization (ATRP), 4‐(2‐bromo‐2‐methylpropionyloxy)‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (Br‐TEMPO), was synthesized by the reaction of 4‐hydroxyl‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy with 2‐bromo‐2‐methylpropionyl bromide. Stable free radical polymerization of styrene was then carried out using a conventional thermal initiator, dibenzoyl peroxide, along with Br‐TEMPO. The obtained polystyrene had an active bromine atom for ATRP at the ω‐end of the chain and was used as the macroinitiator for ATRP of methyl acrylate and ethyl acrylate to prepare block copolymers. The molecular weights of the resulting block copolymers at different monomer conversions shifted to higher molecular weights and increased with monomer conversion. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2468–2475, 2006     

Postfunctionalization of polyoxanorbornene via sequential Michael addition and radical thiol‐ene click reactions

We demonstrated the successful postfunctionalization of poly(oxanorbornene imide) (PONB) with two types of double bonds using sequential orthogonal reactions, nucleophilic thiol‐ene coupling via Michael addition and radical thiol‐ene click reactions. First, the synthesis of PONB with side chain acrylate groups is carried out via ring‐opening metathesis polymerization and nitroxide radical coupling reaction, respectively. Subsequently, the resulting polymer having two different orthogonal functionalities, main chain vinyl and side chain acrylate, is selectively modified via two sequential thiol‐ene click reactions, nucleophilic thiol‐ene coupling via Michael addition and photoinduced radical thiol‐ene. The orthogonal reactivity of two diverse double bonds, vinyl and acrylate functionalities, for the abovementioned consecutive thiol‐ene click reactions was first demonstrated on the model compound. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of palladium complexes with bis(diphenylphosphinomethyl)amino ligands: A catalyst for the Heck reaction of aryl halide with methyl acrylate

A series of ligands, (Ph₂PCH₂)₂NR (R = -CH₃) (1), -C(CH₃)₃, (2) -m-C₆H₄SO₃Na (3), and their Pd(II) complexes have been synthesized under nitrogen atmosphere using Schlenk method. All compounds were characterized using elemental analysis and spectroscopic techniques (AAS, NMR (¹H, ³¹P)). Based on the analysis the complexes have been proposed as in square planar geometry. The Pd(II) complexes were applied to the Heck reaction of aryl halide (Br, Cl) with methyl acrylate. The results have exhibited that complexes [PdCl₂((Ph₂PCH₂)₂NCH₃)] (4) and [PdCl₂((Ph₂PCH₂)₂NC(CH₃)₃)] (5) have shown higher turnover numbers (TON) than complex [PdCl₂(Ph₂PCH₂)₂N-m-C₆H₄SO₃Na] (6).     

Synthesis of bulky tris[(dimethyl(alkyl/aryl)silyl)methyl]stannanes as radical based reducing agents

The synthesis of novel bulky tris[dimethyl(ethyl/benzyl/p-tolyl/α-naphthyl)silylmethyl]stannanes (1-4) is described. Alkylation of SnCl₄ with Me₂(ethyl/p-tolyl)SiCH₂MgBr (10-11) gave mainly the triorganotin chlorides [(Me₂(ethyl/p-tolyl)SiCH₂)]₃SnCl 14 and 15, which were isolated by silica gel chromatography. Reduction of 14 and 15 with LiAlH₄ in THF gave the corresponding triorganotin hydrides 1 and 2, respectively. [Me₂(benzyl/α-naphthyl)SiCH₂]₃SnCl 16 and 17, generated by the alkylation of SnCl₄ with Me₂(benzyl/α-naphthyl)SiCH₂MgBr 12 and 13, were inseparable from the minor product [Me₂(benzyl/α-naphthyl)SiCH₂]₂SnCl₂18 and 19, respectively. Treatment of the mixtures of 16/18 and 17/19 with NaOH furnished the corresponding mixtures of stannoxanes, from which the hexakisdistannoxanes [Me₂(benzyl/α-naphthyl)SiCH₂]₆Sn₂O 20 and 22 were isolated from the minor dialkyltin oxide derivatives [Me₂(benzyl/α-naphthyl)SiCH₂]₂SnO in good yields. Reduction of 20 and 22 with BH₃ in THF gave [Me₂(benzyl/α-naphthyl)SiCH₂]₃SnH (3 and 4), respectively in good yields. ¹H, ¹³C, ¹¹⁹Sn, ²⁹Si NMR characteristics of the newly synthesized compounds are included.     

Synthesis and characterization of fluorinated PEO-b-PDMS-b-fluorinated PEO by free radical addition

Fluorinated poly(ethylene oxide) propyl-b-polydimethylsiloxane-b-propyl fluorinated poly(ethylene oxide)(FPEO-b-PDMS-b-FPEO) was synthesized by a free radical addition of carbon-hydrogen of polyether segments of poly(ethylene oxide) propyl-b-polydimethylsiloxane -b-propyl poly(ethylene oxide)(PEO-b-PDMS-b-PEO) to hexafluoropropylene(HFP) using tert-butyl peroxypivalate as an initiator.In order to reduce the possibility of side reaction,the protection and deprotection via silylation were used for the end-...     

Synthesis of aryl- and hetarylphosphonates

The reaction of tris(trimethylsilyl) phosphite with aryl or hetaryl halides under homogeneous catalysis conditions gave bis(trimethylsilyl)phosphonates. Treatment of these products with methanol gave the corresponding arylor hetarylphosphonic acids in quantitative yield.M. V. Lomonosov Moscow State University, 119899 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2432–2435, October, 1992.     

Synthesis of 1-aryl indoles via coupling reaction of indoles and aryl halides catalyzed by CuI/metformin

Ullmann-type C–N coupling reaction has been developed for the synthesis of 1-aryl indole derivatives by indoles and aryl halides in the presence of CuI/metformin (CuI/Met) in DMF. This method is very easy, rapid, and high yielding reaction for the synthesis of 1-aryl indoles. In particular, the metformin, which is used as ligand, is inexpensive and nontoxic that is considered to be relatively environmentally benign.     

Synthesis of di(2-bromoalkyi) disulfides by electrophilic addition of dithiobisamines to olefins

A new method for the synthesis of di(2-haloalkyl) disulfides and ,'-dibromothiacyclanes was proposed based on reactions of dithiobisamines with olefins in the presence of PBr₃, PBr₅, or POBr₃. Reactions with alkenes lead to di(2-bromoalkyl) disulfides. Analogous products and heterocyclic dibromosulfides,i.e., the products of addition of one dithiobisamine molecule to both double bonds of a diene, are obtained in reactions with alkadienes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2511–2525, October, 1996.     

Synthesis and desilylation of some bis(trimethylsilyl)alkenes and polymers bearing bis(silyl)alkenyl groups

The synthesis of various vinylbis(silanes) from some aryl and heteroaryl aldehydes and (Me₃Si)₃CLi in Et₂O is described. Friedel-Crafts reaction of 1,1-bis(trimethylsilyl)-2-(2-naphthyl)ethene with various acyl chlorides (RCOCl, R = Me, Et, i-Pr, i-Bu, n-pent) gave the corresponding α-silyl-α,β-unsaturated enones with high E steroselectivity. Moreover, poly(styrene)-co-[2,2-bis(trimethylsilyl)ethenyl(styrene)] obtained via the reaction of polymers bearing pendant enone functions and (Me₃Si)₃CLi, reacts with the same acyl chlorides in the presence of catalytic amount of AlCl₃ to give the new macromolecules bearing α-silyl-α,β-unsaturated enones and α,β-unsaturated enones.     

CAN作用下脂肪族含氮化合物的游离基反应研究

使用硝酸高铈铵(CAN)作为氧化剂, 对不同类型的脂肪族含氮化合物的氧化游离基反应进行调查, 对于不同类型的含氮化合物, 得到不同的结果。