Lewis Acid Catalyzed Cascade Reaction to Carbazoles and Naphthalenes via Dehydrative [3 + 3]-Annulation

A novel Lewis acid catalyzed dehydrative [3 + 3]-annulation of readily available benzylic alcohols and propargylic alcohols was developed to give polysubstituted carbazoles and naphthalenes in moderate to good yields with water as the only byproduct. The reaction was presumed to proceed via a cascade process involving Friedel–Crafts-type allenylation, 1,5-hydride shift, 6π-eletrocyclization, and Wagner–Meerwein rearrangement

A Novel Lewis Acid Catalyzed [3 + 3]-Annulation Strategy for the Syntheses of Tetrahydro-β-Carbolines and Tetrahydroisoquinolines

A novel Lewis acid catalyzed [3 + 3]-annulation process for the efficient syntheses of both tetrahydro-β-carbolines and tetrahydroisoquinolines from readily available benzylic alcohols and aziridines was developed, which would be a highly valuable complement to the widely used Pictet–Spengler reaction. A probable mechanism was proposed based on the isolation and characterization of two key intermediates. This strategy enables facile access to important alkaloid frameworks not easily available with other known methods

Reactivity of 3‑Imino-Functionalized Indoles with Rare-Earth-Metal Amides: Unexpected Substituent Effects on C–H Activation Pathways and Assembly of Rare-Earth-Metal Complexes

The reactivities of different 3-imino-functionalized indoles with rare-earth-metal amides [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ were studied to reveal unexpected substituent effects on C–H bond activation pathways, leading to the formation of unusual rare-earth-metal complexes. The reactions of 3-(<i>tert-</i>butylimino)­indole with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ produced tetranuclear rare-earth-metal complexes {[η¹:(μ₂-η¹:η¹):η¹-3-(<i>t</i>BuNCH)­C₈H₄N]­RE₂­(μ₂-Cl)₂(THF)­[N­(SiMe₃)₂]­(η¹:η¹-[μ-η⁵:η²<i>-</i>3-(<i>t</i>BuNCH)­C₈H₅N]₂Li)}₂ (RE = Ho (<b>1a</b>), Er (<b>1b</b>)), incorporating a unique indolyl-1,2-dianion through sp² C–H activation bonded with the central metal in η¹:(μ₂-η¹:η¹) mode. The reactions of 3-(phenylimino)­indole with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ afforded novel binuclear complexes formulated as {3-[PhNCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NRE­(THF)­(μ₂-Cl)­Li­(THF)₂}₂ (RE = Y (<b>2a</b>), Sm (<b>2b</b>), Dy (<b>2c</b>), Yb (<b>2d</b>)) through an unexpected sp³ C–H bond activation with subsequent C–C bond coupling reactions. Treatment of 3-(2-methylphenylimino)­indole or 3-(4-methylphenylimino)­indole with [(Me₃Si)₂N]₃­Yb­(μ-Cl)­Li­(THF)₃ generated the corresponding dinuclear rare-earth-metal amido complexes {3-[(2-MePh)­NCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NYb­(THF)­(μ₂-Cl)­Li­(THF)₂}₂ (<b>3</b>) and {3-[(4-MePh)­NCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NYb­(THF)­(μ₂-Cl)­Li­(THF)₂}₂ (<b>4</b>), following the same pathway for the formation of complexes <b>2a</b>–<b>d</b>. Treatment of 3-(4-<i>tert</i>-butylphenylimino)­indole with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ afforded new hexanuclear rare-earth-metal complexes {3-[(4-^<i>t</i>Bu-Ph)­NHCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NREN­(SiMe₃)₂}₆ (RE = Dy (<b>5a</b>), Ho (<b>5b</b>), Er (<b>5c</b>)) via sp³ C–H bond activation followed by C–C bond coupling reactions. In contrast, under the same conditions as those for the preparation of <b>5</b>, the reaction with the corresponding yttrium complex provided the new heterohexayttrium complex {3-[(4-<i>t</i>Bu-Ph)­NCH­(CH₂SiMe₂)­N­(SiMe₃)]­C₈H₅NYN­(SiMe₃)₂­Li­(THF)}₆ (<b>6</b>), having a 4-<i>t</i>Bu-anilido moiety. All of these complexes were fully characterized by elemental analysis, spectroscopic methods, and X-ray structure analysis. Plausible pathways for the formation of these different rare-earth-metal complexes were proposed

Tris(pyrazolyl)methanide Complexes of Trivalent Rare-Earth Metals

Three types of trivalent rare-earth-metal complexes supported by a monoanionic tris­(pyrazolyl)­methanide ligand were synthesized and structurally characterized, and the catalytic activity of the dialkyl derivatives for isoprene polymerization was investigated. Reactions of the lithium salt of tris­(3,5-dimethylpyrazolyl)­methanide <b>L</b>Li­(THF) with 1 equiv of ScCl₃(THF)₃, YCl₃, or LuCl₃ in THF provided the ion-pair complexes [<b>L</b>LnCl₃]­[Li­(THF)₄] (Ln = Sc (<b>1</b>), Y (<b>2</b>), Lu (<b>3</b>)). Dialkyl complexes <b>L</b>Ln­(CH₂SiMe₃)₂(THF) (Ln = Y (<b>4</b>), Lu (<b>5</b>)) were prepared by salt metathesis of <b>L</b>Li­(THF) with 1 equiv of [Y­(CH₂SiMe₃)₂(THF)₃]­[BPh₄] or [Lu­(CH₂SiMe₃)₂(THF)₃]­[BPh₄] in toluene. Reaction of <b>5</b> with PhSiH₃ provided the unexpected alkylidene-bridged dinuclear complex <b>L</b>₂Lu₂(μ-η¹:η¹-3,5-(CH₃)­C₃HN₂)₂(μ-CHSiMe₃) (<b>6</b>). Complexes <b>1</b>–<b>6</b> were structurally characterized by single-crystal X-ray diffraction, showing that the tris­(pyrazolyl)­methanide ligand acts as a κ³-coordinating six-electron donor in all complexes. The dialkyl complexes catalyzed 1,4-cis polymerization of isoprene with high selectivity upon activation with borate and alkylaluminum

Reactivity of 1,3-Disubstituted Indoles with Lithium Compounds: Substituents and Solvents Effects on Coordination and Reactivity of Resulting 1,3-Disubstituted-2-Indolyl Lithium Complexes

Reactivity of 1,3-disubstituted indolyl compounds with lithium reagents was studied to reveal the substituents and solvent effects on coordination modes and reactivities resulting in different indolyl lithium complexes. Treatment of 1-alkyl-3-imino functionalized compounds 1-R-3-(R′NCH)­C₈H₅N [R = Bn, R′ = Dipp (<b>HL</b>^<b>1</b>); R = Bn, R′ = ^<i>t</i>Bu (<b>HL</b>^<b>2</b>); R = CH₃OCH₂, R′ = Dipp (<b>HL</b>^<b>3</b>); Dipp = ^<i>i</i>Pr₂C₆H₃] with Me₃SiCH₂Li or ^<i>n</i>BuLi in hydrocarbon solvents (toluene or <i>n</i>-hexane) produced 1,3-disubstituted-2-indolyl lithium complexes [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippNCH)­C₈H₄NLi]₂ (<b>1</b>), {[η¹:(μ₃-η¹:η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­[η²:η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­[η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­Li₃} (<b>2</b>), and [η¹:η¹:(μ₂-η¹:η¹)-1-CH₃OCH₂-3-(DippNCH)­C₈H₄NLi]₂ (<b>3</b>), respectively. The bonding modes of the indolyl ligand were kept in <b>1</b> by coordination with donor solvent, affording [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippNCH)­C₈H₄NLi­(THF)]₂ (<b>4</b>). The trinuclear complex <b>2</b> was converted to dinuclear form with a change of bonding modes of the indolyl ligand by treatment of <b>2</b> with donor solvent THF, producing [η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄NLi­(THF)]₂ (<b>5</b>). X-ray diffraction established that compounds <b>1</b>, <b>3</b>, <b>4</b>, and <b>5</b> crystallized as dinuclear structures with the carbanionic sp² carbon atoms of the indolyl ligands coordinated to lithium ions in a μ₂-η¹:η¹ manner, while compound <b>2</b> crystallized as a trinuclear structure and the carbanionic atoms of the indolyl moieties coordinated to lithium ions in μ₂-η¹:η¹ and μ₃-η¹:η¹:η¹ manners. When the lithiation reaction of <b>HL</b>^<b>1</b> with 1 equiv of ^<i>n</i>BuLi was carried out in THF, the monomeric lithium complex {η¹:η¹-1-Bn-3-(DippNCH)-2-[1′-Bn-3′-(DippNCH)­C₈H₅N]­C₈H₄NLi­(THF)} (<b>6</b>) having coupled indolyl moieties was obtained. The compound <b>6</b> can also be prepared by the reaction of <b>1</b> with 0.5 equiv of <b>HL</b>^<b>1</b> with a higher isolated yield. Accordingly, the lithium complexes [η¹:η⁴-1-Bn-3-^<i>t</i>BuNCH-2-(1′-Bn-3′-^<i>t</i>BuNCHC₈H₅N)­C₈H₄NLi­(L)] (L = THF, <b>7a</b>; L = Et₂O, <b>7b</b>) with the coupled indolyl moieties in η⁴ mode were isolated by treatment of <b>HL</b>^<b>2</b> with <b>2</b> in THF or Et₂O. All complexes were characterized by spectroscopic methods, and their structures were determined by X-ray diffraction study

Reactivity of 1,3-Disubstituted Indoles with Lithium Compounds: Substituents and Solvents Effects on Coordination and Reactivity of Resulting 1,3-Disubstituted-2-Indolyl Lithium Complexes

Reactivity of 1,3-disubstituted indolyl compounds with lithium reagents was studied to reveal the substituents and solvent effects on coordination modes and reactivities resulting in different indolyl lithium complexes. Treatment of 1-alkyl-3-imino functionalized compounds 1-R-3-(R′NCH)­C₈H₅N [R = Bn, R′ = Dipp (<b>HL</b>^<b>1</b>); R = Bn, R′ = ^<i>t</i>Bu (<b>HL</b>^<b>2</b>); R = CH₃OCH₂, R′ = Dipp (<b>HL</b>^<b>3</b>); Dipp = ^<i>i</i>Pr₂C₆H₃] with Me₃SiCH₂Li or ^<i>n</i>BuLi in hydrocarbon solvents (toluene or <i>n</i>-hexane) produced 1,3-disubstituted-2-indolyl lithium complexes [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippNCH)­C₈H₄NLi]₂ (<b>1</b>), {[η¹:(μ₃-η¹:η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­[η²:η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­[η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄N]­Li₃} (<b>2</b>), and [η¹:η¹:(μ₂-η¹:η¹)-1-CH₃OCH₂-3-(DippNCH)­C₈H₄NLi]₂ (<b>3</b>), respectively. The bonding modes of the indolyl ligand were kept in <b>1</b> by coordination with donor solvent, affording [η¹:(μ₂-η¹:η¹)-1-Bn-3-(DippNCH)­C₈H₄NLi­(THF)]₂ (<b>4</b>). The trinuclear complex <b>2</b> was converted to dinuclear form with a change of bonding modes of the indolyl ligand by treatment of <b>2</b> with donor solvent THF, producing [η¹:(μ₂-η¹:η¹)-1-Bn-3-(^<i>t</i>BuNCH)­C₈H₄NLi­(THF)]₂ (<b>5</b>). X-ray diffraction established that compounds <b>1</b>, <b>3</b>, <b>4</b>, and <b>5</b> crystallized as dinuclear structures with the carbanionic sp² carbon atoms of the indolyl ligands coordinated to lithium ions in a μ₂-η¹:η¹ manner, while compound <b>2</b> crystallized as a trinuclear structure and the carbanionic atoms of the indolyl moieties coordinated to lithium ions in μ₂-η¹:η¹ and μ₃-η¹:η¹:η¹ manners. When the lithiation reaction of <b>HL</b>^<b>1</b> with 1 equiv of ^<i>n</i>BuLi was carried out in THF, the monomeric lithium complex {η¹:η¹-1-Bn-3-(DippNCH)-2-[1′-Bn-3′-(DippNCH)­C₈H₅N]­C₈H₄NLi­(THF)} (<b>6</b>) having coupled indolyl moieties was obtained. The compound <b>6</b> can also be prepared by the reaction of <b>1</b> with 0.5 equiv of <b>HL</b>^<b>1</b> with a higher isolated yield. Accordingly, the lithium complexes [η¹:η⁴-1-Bn-3-^<i>t</i>BuNCH-2-(1′-Bn-3′-^<i>t</i>BuNCHC₈H₅N)­C₈H₄NLi­(L)] (L = THF, <b>7a</b>; L = Et₂O, <b>7b</b>) with the coupled indolyl moieties in η⁴ mode were isolated by treatment of <b>HL</b>^<b>2</b> with <b>2</b> in THF or Et₂O. All complexes were characterized by spectroscopic methods, and their structures were determined by X-ray diffraction study

Copper(I)-Catalyzed Kinetic Resolution of <i>N</i>‑Sulfonylaziridines with Indoles: Efficient Construction of Pyrroloindolines

The first Lewis acid catalyzed [3 + 2] annulation of indoles and 2-aryl-<i>N</i>-tosylaziridines was realized by using copper­(I)/chiral diphosphine complexes as a catalyst. With this method, a variety of uniquely substituted chiral pyrroloindolines bearing multiple contiguous stereogenic centers were facilely accessed in a straightforward, high-yielding, and highly stereoselective way under mild conditions

Synthesis and Characterization of Rare-Earth Metal Complexes Supported by 2‑Imino or Amino Appended Indolyl Ligands with Diverse Hapticities: Tunable Selective Catalysis for Isoprene Polymerization

The reaction of 2-(2,6-DippNHCH₂)­C₈H₅NH (Dipp = 2,6-^<i>i</i>PrC₆H₃, C₈H₅NH = indolyl) with 1 equiv of (Me₃SiCH₂)₃Yb­(THF)₂ at room temperature generated mononuclear ytterbium complex <b>1</b> having the indolyl ligands in η¹:η¹ mode with reduction of Yb³⁺ to Yb²⁺ and oxidation of the amino to imino group. In the case of Er and Y, the reactions produced dinuclear complexes <b>2</b> and <b>3</b> having the indolyl ligands in μ-η²:η²:η¹ modes with the central metals. When the rare-earth metal is dysprosium, the reaction afforded mixed ligated dinuclear complex <b>4a</b> having indolyl ligands in μ-η⁵:η¹:η¹ and μ-η⁶:η¹:η¹ modes with Dy, and its isomer <b>4b</b> having the indolyl ligands only in μ-η⁵:η¹:η¹ modes with Dy. However, when the rare-earth metal is Gd, the reaction only produced the mixed ligated dinuclear gadolinium complex [(μ-η⁵:η¹:η¹)-2-(2,6-DippNCH₂)­Ind­(μ-η⁶:η¹:η¹)-2-(2,6-DippNCH₂)­Ind]­[Gd­(CH₂SiMe₃)­(thf)]₂ (<b>5</b>), having indolyl ligands in μ-η⁵:η¹:η¹ and μ-η⁶:η¹:η¹ modes with Gd. In addition, treatment of 2-(2,6-DippNHCH₂)­C₈H₅NH with 1.25 equiv of (Me₃SiCH₂)₃Gd­(THF)₂ produced the alkoxido-bridged trinuclear gadolinium complex [(μ-η³:η²:η¹:η¹)-2-(2,6-DippNCH₂)­Ind­(μ-η²:η¹:η¹)-2-(2,6-DippNCH₂)­Ind<i>-</i>(η¹:η¹)-2-(2,6-DippNCH₂)­Ind]-Gd₃[(μ₃<i>-</i>O­(CH₂)₅SiMe₃)­(μ₂-O­(CH₂)₅SiMe₃)­(thf)₃] (<b>6</b>) having indolyl ligands in η¹:η¹, μ-η²:η¹:η¹, and μ-η³:η²:η¹:η ¹ modes with metals, respectively. In complex <b>6</b>, sp² C–H activation is observed at the 7-indolyl position producing unique 2-amido substituted indolyl-1,7-dianions having a μ-η³:η²:η¹:η¹ bonding modes with three metals. The O­(CH₂)₅SiMe₃ arises from the ring-opening of THF by attack of CH₂SiMe₃. Moreover, when 2-(2,6-DippNHCH₂)­C₈H₅NH was treated with 1 equiv of (Me₃SiCH₂)₃Sm­(THF)₂, a dinuclear samarium complex [μ-η³:η¹:η¹-2-(2,6-DippNCH₂)­Ind]₃Sm₂(thf)₃ (<b>7</b>) having a bridged indolyl ligand in μ-η³:η¹:η¹ hapticities was isolated. All structures of the complexes have been determined by X-ray crystallographic analyses. Dinuclear alkyl complexes <b>2</b>–<b>5</b> have been tested as isoprene polymerization initiators in the presence of Al^<i>i</i>Bu₃ and [Ph₃C]­[B­(C₆F₅)₄]. The regioselectivity for isoprene polymerization is tunable from 1,4-<i>cis</i> (up to 93.5%) to 3,4- (up to 86.2%) selectivity by these catalysts simply by adjusting the addition order of Al^<i>i</i>Bu₃ and [Ph₃C]­[B­(C₆F₅)₄]

CNC-Pincer Rare-Earth Metal Amido Complexes with a Diarylamido Linked Biscarbene Ligand: Synthesis, Characterization, and Catalytic Activity

In preparation of CNC-pincer rare-earth metal amido complexes with a diarylamido linked biscarbene ligand, it is found that conditions have a key influence on final products. Reaction of a THF suspension of bis­[2-(3-benzyl­imidazolium)-4-methyl­phenyl]­amine dichlorides (H₃<b>L</b>Cl₂) with [(Me₃Si)₂­N]₃­RE­(μ-Cl)­Li­(THF)₃ (RE = Yb, Eu, Sm) in THF at room temperature afforded the only unexpected fused-heterocyclic compound 8,9-dibenzyl-3,14-dimethyl-8<i>a</i>,9-dihydro-8<i>H</i>-benzo­[4,5]­imidazo­[2′,1′:2,3]­imidazo­[1,2-<i>a</i>]­imidazo­[2,1-<i>c</i>]­quinoxaline (<b>1</b>) containing an imidazolyl ring and a piperidyl ring, which formed through carbene C–C and C–N coupling. However, the reaction of H₃<b>L</b>Cl₂ with [(Me₃Si)₂­N]₃­Er­(μ-Cl)­Li­(THF)₃ in toluene afforded the CNC-pincer erbium amido complex incorporating a diarylamido linked biscarbene ligand <b>L</b>Er­[N­(SiMe₃)₂]₂ (<b>2</b>) in low yield and the above fused-heterocyclic compound <b>1</b>. The stepwise reaction of H₃<b>L</b>Cl₂ with strong bases (<i>n</i>-BuLi or LiCH₂SiMe₃) in THF for 4 h, followed by treatment with [(Me₃Si)₂­N]₃­RE­(μ-Cl)­Li­(THF)₃, generated zwitterion complexes [<b>L</b>₂RE]­[RECl­{N­(SiMe₃)₂}₃] (<b>L</b> = [4-CH₃-2-{(C₆H₄CH₂-[N­(CH)₂­CN]}­C₆H₃]₂N; RE = Y (<b>3</b>), Er (<b>4</b>), Yb (<b>5</b>)) in less than 20% yields together with fused-heterocyclic compound <b>1</b>. Additionally, the reaction of H₃<b>L</b>Cl₂ with 6 equiv of NaN­(SiMe₃)₂ in THF for 4 h, followed by treatment with YbCl₃, generated a novel discrete complex [<b>L</b>₂Yb]­[{Na­(μ-N­(SiMe₃)₂)}₅­(μ₅-Cl)] (<b>6</b>). The one-pot reaction of H₃<b>L</b>Cl₂ with <i>n</i>-BuLi, followed by reaction with [(Me₃Si)₂­N]₃­RE­(μ-Cl)­Li­(THF)₃ in THF at −78 °C, generated the CNC-pincer lanthanide bisamido complexes <b>L</b>RE­[N­(SiMe₃)₂]₂ (RE = Er (<b>2</b>), Y (<b>7</b>), Sm (<b>8</b>), Eu (<b>9</b>)) in moderate yields. These kinds of biscarbene supported pincer bisamido complexes could also be prepared by a one-pot reaction of bis­(imidazolium) salt (H₃<b>L</b>Cl₂) with 5 equiv of NaN­(SiMe₃)₂, followed by treatment with RECl₃, in good yields at −78 °C. Investigation of the catalytic activity of complexes <b>2</b> and <b>7</b>–<b>9</b> indicated that all complexes showed a high activity toward the addition of terminal alkynes to carbodiimides producing propiolimidines, which represents the first example of rare-earth metal CNC-pincer-type catalysts applied for catalytic C–H bond addition of terminal alkynes to carbodiimides at room temperature

Aluminum Complexes Bearing N‑Protected 2‑Amino- or 2‑Imino-Functionalized Pyrrolyl Ligands: Synthesis, Structure, and Catalysis for Preparation of Pyrrolyl-End-Functionalized Polyesters

Reactivity of N-protected 2-amino- or 2-imino-functionalized pyrroles with aluminum alkyls was investigated, resulting in the isolation of a series of aluminum alkyl complexes. Treatment of 2-imino-functionalized pyrrole with AlMe₃ produced only imino-coordinated aluminum complex 1-Bn-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­C₄H₃NAlMe₃ (<b>1</b>), while reactions of N-protected 2-amino-functionalized pyrroles with aluminum alkyls produced the aluminum alkyl complexes {[η¹-μ-η¹:η¹-1-R₁-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH₂)­C₄H₂N]­AlR}₂ (R₁ = Bn, R = Me (<b>2</b>); R₁ = Bn, R = Et (<b>3</b>); R₁ = R = Me (<b>4</b>); R₁ = Me, R = Et (<b>5</b>)), bearing 3-carbon bonded pyrrolyl ligands via C–H σ-bond metathesis reaction. Further reactions of complexes <b>2</b>–<b>5</b> with a stoichiometric amount of isopropyl alcohol (^<i>i</i>PrOH) afforded the corresponding aluminum alkoxide complexes [1-R₁-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH₂)­C₄H₃NAlR­(μ-O^<i>i</i>Pr)]₂ (R₁ = Bn, R = Me (<b>6</b>); R₁ = Bn, R = Et (<b>7</b>); R₁ = R = Me (<b>8</b>); R₁ = Me, R = Et (<b>9</b>)) through selective cleavage of the Al–C (Pyr) bonds. The solid-state structures of the aluminum complexes <b>1</b>–<b>6</b> and <b>8</b> were confirmed by an X-ray diffraction study. These aluminum alkyl complexes exhibited notable activity toward the ring-opening polymerization of ε-caprolactone and l-lactide in the absence of alcohol. The end group analysis of the ε-CL oligomer gave strong support that the polymerization proceeded via a coordination–insertion mechanism involving a unique Al–C (Pyr) bond initiation, providing pyrrolyl-end-functionalized polyesters