Crystal structure of an uncomplexed 25-crown-7 comprising one 2,6-pyridino and two 1,4-benzo condensations

Single crystal X-ray analysis of the uncomplexed crown macroring 1 is reported. Crystals are triclinic, , witha=10.809(1),b=10.945(1),c=10.256(1) Å, =107.85(1), =104.15(1), =87.27(1)°,D _c=1.318 g cm^–3,Z=2. Three torsion angles in the macrocycle take upgauche conformations in contrast to the usualanti conformation. The crystal structure is stabilized by intramolecular van der Waals forces and weak C–H...O and C–H...N hydrogen bond attractions. Stacking of pyridine rings is a noticeable packing feature in the crystal lattice. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82168 (6 pages).Macroring Uncharged Molecule Complexation. Part 20. For Part 19 of this series see Ref. [1].     

Rhodium-catalyzed one-pot synthesis of substituted pyridine derivatives from alpha,beta-unsaturated ketoximes and alkynes

A rhodium-catalyzed chelation-assisted C-H activation of alpha,beta-unsaturated ketoximes and the reaction with alkynes to afford highly substituted pyridine derivatives is described.     

Platinum-catalyzed multistep reactions of indoles with alkynyl alcohols

PtCl2 effectively catalyzes the multistep reaction of N-methyl indole (1 a) with pent-3-yn-1-ol (2 a) in THF at room temperature for 2 h to give indole derivative 3 a, which contains a five-membered cyclic ether group at C3 in 93% yield. Under similar reaction conditions, various substituted N-methyl indoles 1 b-h and indole (1 i) reacted efficiently with 2 a to afford the corresponding indole derivatives 3 b-h and 3 i in 48-91 and 72% yields. The results showed that N-methyl indoles with electron-donating substituents were more reactive affording higher product yields than those with electron-withdrawing groups. Likewise, various substituted but-3-yn-1-ols 2 b-e and other longer chain alkynyl alcohols 2 f-i also underwent a cyclization-addition reaction with N-methyl indole (1 a) to provide the corresponding cyclization-addition products 3 j-m and 3 a, 3 j, and 3 n-o in good to excellent yields. The present platinum-catalyzed cyclization-addition reaction can be further extended into N-methyl pyrrole. Mechanistically, the catalytic reaction proceeds by an intramolecular hydroalkoxylation of alkynyl alcohol to afford cyclic enol ether followed by the addition of the C--H bond of indole to the unsaturated moiety of cyclic enol ether providing the final product. Experimental evidence to support this proposed mechanism is provided.     

Highly efficient cyclization of o-iodobenzoates with aldehydes catalyzed by cobalt bidentate phosphine complexes: a novel entry to chiral phthalides

Methyl 2-iodobenzoates 1 a-c undergo cyclization reactions with various aromatic aldehydes 2 a-m (RC6H4CHO: R=H 2 a, 4-CH3 2 b, 4-tBu 2 c, 4-OMe 2 d, 3-OMe 2 e, 4-Cl 2 f, 4-CF3 2 g, 4-CN 2 h, 4-Ph 2 i; benzo[d][1,3]dioxole-5-carbaldehyde (2 j), 1-napthaldehyde (2 k), benzofuran-2-carbaldehyde (2 l), and isonicotinaldehyde (2 m)) in the presence of [CoI2(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) and Zn powder in dry THF at 75 degrees C for 24 h to give the corresponding phthalide derivatives 3 a-m and 3 q-t in good to excellent yields. Under similar reaction conditions, less reactive aliphatic aldehydes, heptanal (2 n), butyraldehyde (2 o), and 2-phenylacetaldehyde (2 p) also underwent cyclization reactions with 1 a to provide 3 n-p, respectively, in fair to good yields. The catalytic reaction can be further extended to cinnamyl aldehyde (2 q) with 1 a to give the corresponding phthalide derivative 3 u. This synthetic method is compatible with a variety of functional groups on the aryl ring of 2. The high efficiency of the cobalt catalyst containing a dppe (dppe=1,2-bis(diphenylphosphino)ethane) ligand encouraged us to investigate the asymmetric version of the present catalytic reaction by employing bidentate chiral ligands. Thus, aromatic aldehydes 2 a-c, 2 f, and 2 g undergo cyclization with 2-iodobenzoate (1 a) smoothly in the presence of [CoI2{(S,S)-dipamp}] ((S,S)-dipamp=(1S,2S)-(+)-bis[2-methoxyphenyl]phenylphosphino)ethane) and zinc powder in THF at 75 degrees C for 24 h, giving the corresponding (S)-phthalides 4 a-e in 81-89% yields with 70-98% ee. A possible mechanism for the present catalytic reaction is proposed.     

Transition metal-catalyzed three-component coupling of allenes and the related allylation reactions

The feature article surveys the transition metal-catalyzed three-component coupling of allenes and the related allylation reactions. Most of the reactions shown in the article mechanistically proceed via oxidative addition of organic electrophiles to metals, followed by carbometallation of allene and then transmetalation by main group metals or reagents and organometallic reagents. These reactions provide an efficient route for the synthesis of various substituted allyl and vinyl metal reagents and complex organic molecules in highly regio-, stereo- and chemoselective manner in one pot. The metal reagents or pi-allyl-metal intermediates obtained from the reaction are utilized for the allylation of aldehydes, ketones and imines, producing various homoallylic alcohols and amines in a highly regio- and stereoselective manner.     

Copper-catalyzed three-component coupling of arynes, terminal alkynes and activated alkenes

The three-component coupling of benzynes with terminal alkynes and activated alkenes in the presence of CuI, PCy(3) and CsF in a 1:1 mixture of CH(3)CN and THF at 50 degrees C for 5 h gave 1-alkyl-2-alkynylbenzenes in good to moderate yields.     

Cobalt-catalyzed intramolecular [2 + 2 + 2] cocyclotrimerization of nitrilediynes: an efficient route to tetra- and pentacyclic pyridine derivatives

[reaction: see text] In this paper, we wish to report the intramolecular [2 + 2 + 2] cocyclotrimerization of nitrilediynes catalyzed by the CoI2(dppe)/Zn system at 80 degrees C in CH3CN. Under these reaction conditions, various highly substituted nitrilediynes having steric conjunction at the alpha and beta positions to a nitrile group and a bulkier substitution at the terminal carbon of alkyne undergo [2 + 2 + 2] cocylotrimerization to afford tetra- and pentacyclic pyridine derivatives in good to excellent yields.     

Platinum‐Catalyzed Multi‐Step Reaction of Propargyl Alcohols with N‐Heteroaromatics

N‐Methyl indole reacts with but‐2‐yn‐1‐ol in the presence of PtCl₂ in MeOH giving indole derivatives having a substituted 3‐oxobutyl group at the 3‐position in good yield. Under the reaction conditions, various substituted indoles and substituted propargyl alcohols are successfully involved in the reaction giving the corresponding addition products in good to moderate yields. The catalytic reaction can be further extended to N‐phenyl pyrrole. In the present multi‐step reaction, PtCl₂ likely plays dual roles: as the catalyst for the rearrangement of propargyl alcohols to the corresponding alkenyl ketones and as the catalyst for the addition of indoles to the alkenyl ketones. Experimental evidence is provided to support the proposed mechanism.     

Ruthenium-catalyzed regioselective oxidative coupling of aromatic and heteroaromatic esters with alkenes under an open atmosphere

A ruthenium-catalyzed oxidative coupling of substituted aromatic and heteroaromatic esters with alkenes in the presence of catalytic amounts of AgSbF(6) and Cu(OAc)(2) to provide highly substituted alkene derivatives in good to excellent yields under an open atmosphere is described.