- Enantioselective [3 + 2] annulation of 4-isothiocyanato pyrazolones and alkynyl ketones under organocatalysis
-
An asymmetric [3 + 2] annulation reaction of 4-isothiocyanato pyrazolones with alkynyl ketones in the presence of an organic catalyst derived from a cinchona alkaloid under mild conditions is realized. This protocol provides unprecedented expeditious access to a wide range of optically active spiro[pyrroline-pyrazolones] with various electronic properties in high yields with good to excellent enantioselectivities.
- Wang, Wenyao,Wei, Shiqiang,Bao, Xiaoze,Nawaz, Shah,Qu, Jingping,Wang, Baomin
-
p. 1145 - 1154
(2021/02/16)
-
- C-F bond cleavage enabled redox-neutral [4+1] annulation via C-H bond activation
-
Using α,α-difluoromethylene alkyne as a nontraditional one-carbon reaction partner, a synthetically novel method for the construction of isoindolin-1-one derivatives via Rh(III)-catalyzed [4+1] annulation reaction is reported. The 2-fold C-F bond cleavage not only enables the generation of desired product under an overall oxidant-free condition but also results in a net migration of carbon-carbon triple bond. In addition, the present reaction protocol exhibits a tolerance of a wide spectrum of functional groups due to the mild reaction conditions employed.
- Wang, Cheng-Qiang,Ye, Lu,Feng, Chao,Loh, Teck-Peng
-
supporting information
p. 1762 - 1765
(2017/02/15)
-
- Synthesis of Alkylidene(gem-Difluorocyclopropanes) from Propargyl Glycolates by a One-Pot Difluorocyclopropenation/Ireland-Claisen Rearrangement Sequence
-
A one-pot difluorocyclopropenation/Ireland-Claisen rearrangement sequence applied to readily available propargyl glycolates was developed as a route toward functionalized alkylidene(gem-difluorocyclopropanes). This strategy conveniently avoids the isolation of the unstable 3,3-difluorocyclopropenylcarbinyl glycolates arising from the difluorocyclopropenation. The Ireland-Claisen rearrangement proceeds with high diastereoselectivity and chirality transfer to afford alkylidene(gem-difluorocyclopropanes) incorporating a quaternary stereocenter and a protected glycolic acid moiety, which are useful building blocks for the preparation of functionalized gem-difluorocyclopropanes.
- Ernouf, Guillaume,Brayer, Jean-Louis,Folléas, Beno?t,Demoute, Jean-Pierre,Meyer, Christophe,Cossy, Janine
-
p. 3965 - 3975
(2017/04/11)
-
- Copper(I)-catalyzed regio- and stereoselective intramolecular alkylboration of propargyl ethers and amines
-
The copper(I)-catalyzed regio- and stereoselective intramolecular alkylation of propargyl ethers and amines bearing an alkyl electrophilic moiety has been developed. The reaction showed high functional group tolerance and gave highly functionalized alkenylboronates bearing heterocyclic rings, which are versatile synthetic intermediates in organic chemistry. The borylation products can be transformed into multisubstituted alkenes through stereospecific transformations. Mechanistic studies showed that the chemo- and stereoselectivity of copper(I)-catalyzed borylation depends on the type of leaving group. Density functional theory calculations suggested that the regioselectivity of the borylcupration of the alkyne is controlled by the electronic effect of the oxygen atom of the propargyl ether in combination with the steric congestion between the boryl group and the substituent at the propargylic position.
- Iwamoto, Hiroaki,Ozawa, Yu,Kubota, Koji,Ito, Hajime
-
p. 10563 - 10573
(2018/05/31)
-
- Catalytic Nucleophilic Fluorination of Secondary and Tertiary Propargylic Electrophiles with a Copper-N-Heterocyclic Carbene Complex
-
A catalytic method for the nucleophilic fluorination of propargylic electrophiles is described. Our protocol involves the use of a Cu(NHC) complex as the catalyst and is suitable for the preparation of secondary and tertiary propargylic fluorides without
- Cheng, Li-Jie,Cordier, Christopher J.
-
supporting information
p. 13734 - 13738
(2015/11/11)
-
- One-pot synthesis of optically active allyl esters via lipase-vanadium combo catalysis
-
The combination of vanadium-oxo compounds (3 or 4) with a lipase produced the regio- and enantioconvergent transformation of racemic allyl alcohols (1 or 2) into optically active allyl esters. In this system, the vanadium compounds catalyzed the continuous racemization of the alcohols along with the transposition of the hydroxyl group, while the lipase effected the chemo- and enantioselective esterification to achieve the dynamic kinetic resolution.
- Akai, Shuji,Hanada, Ryosuke,Fujiwara, Noboru,Kita, Yasuyuki,Egi, Masahiro
-
supporting information; experimental part
p. 4900 - 4903
(2011/01/12)
-
- Formation of chiral C(sp3)-C(sp) bond by allylic substitution of secondary allylic picolinates and alkynyl copper reagents
-
(Chemical Equation Presented) To establish allylic substitution of secondary allylic alcohol derivatives with alkynyl copper reagents, allylic esters bearing the (2-pyridine)CO2-, (2-pyrazine)CO2-, (EtO)2PO2-, C6F5CO2-, o-(Ph2P)-C6H4CO2-, MeOCO 2-, or. AcO- group were examined. First, picolinate (R 1=Me, R2=CH2OPMB) was subjected to reaction with (TMS-C≡C)2CuLi 3 LiBr at 0 °C. Although no substitution took place, MgBr2 (3 equiv) was found to promote the reaction to produce the anti SN2′ product in 93% yield with 94% regioselectivity and 99% chirality transfer. In contrast, substitution of the other esters with the copper reagent in the presence of MgBr2 were less reactive ((2-pyrazine)CO2-) or marginally reactive (other cases). Generality of the substitution using picolinates was established with five picolinates (R1=Me, Ph(CH2)2, PMBO(CH 2)3; R2=Me, CH2OPMB, CH 2OTBS, C5H11, c-C6H11) and seven alkynyl copper reagents (R3=TMS, Ph, p-TBSOC 6H4, p- and o-MeOC6H4, p-MeC 6H4, p-FC6H4), furnishing anti SN2′ products in 61-93% yields with high regioselectivity (usually >90%) and high chirality transfer (usually >95%). In addition, transformation of the products was briefly studied. 2009 American Chemical Society.
- Kiyotsuka, Yohei,Kobayashi, Yuichi
-
supporting information; experimental part
p. 7489 - 7495
(2010/01/06)
-
- Electrophilic fluorodesilylation of allenylmethylsilanes: A novel entry to 2-fluoro-1,3-dienes
-
(Chemical Equation Presented) Various fluorodienes were prepared by treatment of the corresponding allenylmethylsilanes with Selectfluor. This is the first route to these compounds not based on the use of a fluorinated building block. The reaction allows
- Pacheco, Ma. Carmen,Gouverneur, Veronique
-
p. 1267 - 1270
(2007/10/03)
-