Synthesis of the C1-C12 acid fragment of amphidinolide T marine macrolides via SmI2-mediated enantioselective reductive coupling of aldehydes with a chiral crotonate

A new strategy for enantioselective assembly of the trisubstituted tetrahydrofuran ring has been established for synthesis of the C1-C12 acid fragment of amphidinolide T series marine macrolides. The key steps involve the SmI₂-mediated highly enantioselective reductive coupling of an aldehyde with the (1S,2R)-N-methylephedrine-derived crotonate to form the cis-3,4-disubstituted γ-butyrolactone and the subsequent BF₃-mediated 1,3-anti-selective allylation of the five-membered-ring oxocarbenium ion with allyltrimethylsilane. The desired C1-C12 acid fragment was obtained in >25% overall yield via a 9-step sequence.     

Synthesis of the C1-C12 fragment of amphidinolide T1

A synthesis of the C1-C12 fragment of amphidinolide T1 utilising Evans’ aldol, oxy-Michael and cross metathesis reactions as the key steps is described.     

Nickel-catalyzed multi-component coupling reaction of aldimine, alkyne, and dimethylzinc via dimerization of butadiene

In the presence of a Ni/phosphine ligand catalyst, dimethylzinc, alkyne, butadiene, aldehyde, and primary amine were successively combined via dimerization of butadiene to provide (3E,7E,10Z)-dodecatrienylamine in good yields with excellent regio and stereoselectivities.     

Synthesis of polynorbornene with pendant moiety bearing azide and terminal alkyne groups

A powerful approach to the synthesis of an unprecedented polynorbornene with pendant moiety bearing azide and terminal alkyne groups is developed.Two key intermediates,namely,3-azido-5-(2-(trimethylsilyl)ethynyl) benzyl alcohol and 4-(4-azatricyclo [5.2.1.0~(2.6)]dec-8-en-4-yl) benzoic acid,were optimally synthesized for convergent synthesis of the corresponding monomer.     

Synthesis of novel pyrazoles via [2+3]-dipolar cycloaddition using alkyne surrogates

The syntheses of an important class of hitherto unreported novel pyrazoles are described. The regioselective synthesis of 1,3,4,5-tetrasubstituted pyrazoles was achieved by the Huisgen cyclization of nitrile imines with a trisubstituted bromoalkene. The substituted bromoalkene functions as an alkyne synthon which was used to construct 5,5-disubstituted bromopyrazoline intermediates that undergo aromatization to the analogous pyrazoles through the loss of HBr. The cycloaddition regioselectivity was confirmed through single X-ray crystal data of one of the pyrazoles.     

Synthesis of the C(18)-C(34) fragment of amphidinolide C and the C(18)-C(29) fragment of amphidinolide F

A convergent synthesis of the C(18)-C(34) fragment of amphidinolide C and the C(18)-C(29) fragment of amphidinolide F is reported. The approach involves the synthesis of the common intermediate tetrahydrofuranyl-β-ketophosphonate via cross metathesis, Pd(0)-catalyzed cyclization, and hydroboration-oxidation. The β-ketophosphonate was coupled to three side chain aldehydes using a Horner-Wadsworth-Emmons (HWE) olefination reaction to give dienones, which were reduced with l-selectride to give the fragments of amphidinolide C and F.     

Synthesis of 5-functionalized-1,2,3-triazoles via a one-pot aerobic oxidative coupling reaction of alkynes and azides

In this paper, an efficient synthesis of 5-alkynyl-1,2,3-triazoles through a one-pot aerobic oxidative coupling reaction of various alkynes and azides has been developed. Further derivatization of 5-alkynyl-1,2,3-triazoles readily yielded 5-carbonyl-1,2,3-triazoles, 5-carboxylic-1,2,3-triazole, 5-hydroxyalkyl-1,2,3-triazoles and 5-quinoxaline-1,2,3-triazole, which provided an entry into structurally diverse 5-functionalized-1,2,3-triazoles.     

Efficient synthesis of [2]- and higher order rotaxanes via the transition metal-catalyzed hydrosilylation of alkyne

A novel end-capping method of pseudorotaxanes via the hydrosilylation of the alkyne of the axle terminal was developed. RuHCl(CO)(PPh₃)₃ and RhCl(CO)(PPh₃)₃ complexes catalyzed the hydrosilylation reactions of the alkyne moiety of several pseudorotaxanes at ambient temperature to give the corresponding [2]- and higher order rotaxanes in high yields with excellent regio- and stereoselectivity.     

Synthesis of 5-functionalized-1,2,3-triazoles via a one-pot aerobic oxidative coupling reaction of alkynes and azicles

In this paper, an efficient synthesis of 5-alkynyl-1,2,3-triazoles through a one-pot aerobic oxidative coupling reaction of various alkynes and azides has been developed. Further derivatization of 5-alkynyl-1,2,3-triazoles readily yielded 5-carbonyl-1,2,3-triazoles, 5-carboxylic-1,2,3-triazole, 5-hydroxyalkyl-1,2,3-triazoles and 5-quinoxaline-1,2,3-triazole, which provided an entry into structurally diverse 5-functionalized-1,2,3-triazoles.     

One-pot synthesis of 2,4-disubstituted quinolines via silver-catalyzed three-component cascade annulation of amines,alkyne esters and terminal alkynes

Described herein is a new and general method for one-pot synthesis of 2,4-disubstituted quinolines via silver-catalyzed [3?+?1?+?2] annulation of simple amines, alkyne esters and terminal alkynes. The versatile transformation might initiate with the facile formation of the enamine species with the feature of good to excellent yields, exclusive regioselectivity, and excellent substrate/functional group tolerance.     

Synthesis of diaryl disulfides via the reductive coupling of arylsulfonyl chlorides

A facile synthesis of diaryl disulfides from arylsulfonyl chlorides in the presence of triphenylphosphine has been developed.     

Synthesis of a new siladigermirane via an intramolecular reductive cyclization

Si,Si-diphenyltetramesitylsiladigermirane was synthesized via the intramolecular reductive cyclization of bis(chlorodimesitylgermyl)diphenylsilane using t-BuLi or Rieke magnesium. Addition of water to the siladigermirane resulted in regioselective hydrolysis of the siladigermirane to give 1-(hydroxydiphenylsilyl)-1,1,2,2-tetramesityldigermane.     

Synthesis of macrolide antibiotics. 16. Synthesis of erythronolides A and B by a coupling scheme of (C5-C9) + (C3-C4) + (C1-C2) + (C10) + (C11-C13) fragments and synthesis of the C5-C9 fragment

Conclusions A synthesis of a C⁵-C⁹-fragment common to erythronolides A and B was carried out starting from levoglucosan.For previous communications, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 674–680, March, 1989.     

Synthesis and structure of an air-stable bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate and its application in catalytic epoxide ring-opening reactions

An air-stable mononuclear complex of bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate was successfully synthesized by treating C₆F₅SO₃Ag with [(CH₃)₅Cp]₂ZrCl₂, which showed the cationic uninuclear structure of [{(CH₃)₅Cp}₂Zr(CH₃CN)₂(H₂O)][OSO₂C₆F₅]₂·CH₃CN (1) confirmed by the X-ray analysis. Complex 1 was also characterized by other techniques and found to have the good nature of air-stability, water tolerance, thermally-stability and strong Lewis-acidity. Moreover, the complex showed high catalytic activity and recyclability in catalytic epoxide ring-opening reactions by amines or alcohols. This catalytic system affords a simple and efficient approach for synthesis of β-amino alcohols or β-alkoxy alcohols.     

Synthesis of 10,11-dihydroleukotriene B(4) metabolites via a nickel-catalyzed coupling reaction of cis-bromides and trans-alkenyl borates

Synthesis of 10,11-dihydro-, 10,11,14,15-tetrahydro-, and 10, 11-dihydro-12-oxoleukotriene B(4) compounds (2, 4, 5) was accomplished stereoselectively by using the nickel-catalyzed coupling reaction illustrated in Scheme 1. The C(1)-C(7) fragments, TBS ether 10a for 2 and 4 and ethyoxyethyl (EE) ether 10b for 5, were prepared in enantiomerically pure forms (>99% ee) by a modified literature procedure (ref 11a). On the other hand, boronate esters 11a and 11b, which correspond to the C(8)-C(20) parts of 2 and 4, respectively, were synthesized from (R)-epichlorohydrin (18) of 99% ee. Briefly, 18 was converted into acetylenes 24 and 32 through epoxide ring-opening with LiC triple bond CC(5)H(11)/BF(3).OEt(2) or C(7)H(15)MgBr/CuCN. Hydroboration of these acetylenes with (+)-(Ipc)(2)BH followed by reaction with MeCHO afforded the corresponding diethyl boronates, which upon ligand exchange with Me(2)C(CH(2)OH)(2) furnished boronate esters 11a and 11b in 75% and 77% yields, respectively. In a similar manner, racemic boronate ester rac-11a, an intermediate for synthesis of 5, was prepared from racemic epichlorohydrin. For synthesis of 2, borate 25 was generated from 11a (1.5 equiv) and MeLi (1.6 equiv). Without isolation, 25 was submitted to reaction with 10a (1 equiv) in the presence of a Ni(0) species at room temperature overnight to afford 26, which upon treatment with TBAF furnished 2 in 64% yield from 10a. Similarly, 11b and 10a furnished 4 in good yield. To synthesize 5, rac-11a and EE ether 10b were joined by the coupling reaction to produce 39, which was transformed into 40 by desilylation with TBAF. After hydrolysis of 40, oxidation with PDC followed by deprotection of the EE group furnished 5 in 36% yield from 40. In addition, 2 was converted into amide 3 in 92% yield.     

Microwave-assisted decarboxylative three-component coupling of a 2-oxoacetic acid, an amine, and an alkyne

A novel and efficient microwave-assisted decarboxylative three-component coupling of a 2-oxoacetic acid, an amine, and an alkyne (OA(2)-coulpling) has been developed. This new multicomponent coupling constitutes an efficient approach for the synthesis of polysubstituted propargylamines in the presence of a catalytic amount of copper(I) catalyst.     

Synthesis and X-ray structure of C2-C84(22)(CF3)6

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Synthesis of the C10-C22 bis-spiroacetal domain of spirolides B and D via iterative oxidative radical cyclization

[reaction: see text] A synthetic approach to the novel bis-spiroacetal moiety of spirolides B and D is reported. The strategy hinges upon successive formation of the spirocenters at C15 and C18 by radical oxidative cyclization, followed by base-induced rearrangement of a C19-20 alpha-epoxide to introduce the C19 hydroxyl group.     

Synthesis of homo-propargylic ethers: A domino ring opening/coupling reaction of oxiranes with terminal alkynes and aryl iodides

A domino ring opening/cross-coupling reaction of oxiranes with terminal alkynes and aryl iodides has been developed. This transformation serves as a protocol for the synthesis of homo-alkyne ether skeletons from the readily available starting materials. The success of the reaction has dependence on catalyst/ligand system of choice. The synthesis utility of the alkyne ether skeletons in formation of chromane skeleton has also been studied.     

Synthesis of macrolide antibiotics Communication 2. Synthesis of the C9-C13 fragment of erythronolides A and C and megalonolide

Conclusions The synthesis of the C⁹-C¹³ fragment of erythromycin A has been accomplished, starting from levoglusan (18 steps, 3.4%).For previous communications, see [1, 2].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2561–2568, November, 1982.