Yu-Lin Jiang

A Convenient Route to Condensed-Ring Aromatic Acetylenes

Abstract Palladium catalysed coupling of aryl halides with 3-methylbut-1-yn-3-ol and a subsequent base-induced retro-Favorsky reaction gave the corresponding ethynyl aromatics in good to excellent yields.

Elaboration of the side-chain of amino acid derivatives by palladium catalysed couplings

Abstract The palladium-catalysed couplings of aryl halides and triflates with propargyl amino amides and the couplings of aryl and vinyl halides and triflates with an ethynyl oxazolidine are reported.

Intramolecular hydrogen bonding of nucleobases

The intramolecular hydrogen bonding of a series of linked uracil, thymine and adenine derivatives is described. The nucleoside bases have been linked by semi-flexible spacers and the chemical shifts and ΔδNH/ΔT values for the nucleoside NH protons confirm the strong intramolecular hydrogen bonding motif.

INTRAMOLECULAR HYDROGEN BONDING STUDIES FOR A SERIES OF DIPURINYL-2,6-PYRIDINEDICARBOXAMIDES

Abstract A series of potential receptor molecules based on the dipurinyl-2,6-pyridinedicarboxamide motif has been prepared and the intramolecular hydrogen bonding characterised by 1 H NMR and FT-IR spectroscopies. The hydrogen bonding gives rise to a preferential planar, cis conformation for the molecules. The planar nature of the unit also gives rise to π-π stacking as shown by 1 H NMR dilution experiments.

Crystal structure of 1,8-bis[2-(6-methoxy-2-naphthyl)ethynyl]-naphthalene, C36H24O2

Source of material: The titled tweezer-shaped compound (see ref. 1 ) is the by-product of the palladium catalysed coupling reaction (see ref. 2) between 1,8-diiodo-naphthalene with 2-ethynyI-6meth-oxy-naphthalene (see ref. 3) to prepare l-iodo-8-[2-(6-methoxy-2-naphthyl)-ethynyI]naphthalene. The crystals were obtained from the slow evaporation of a dichloromethane solution of the compound; mp 442 К 443 К. The two methoxy naphthyl groups form dihedral angles of 73.8° and 73.6°, respectively, with the bridging naphthyl group; a planar arrangement is precluded owing to steric reasons. The dihedral angle between the two methoxy naphthyl groups is 1.4° and the average separation between them is 3.461 Â indicating π-π interactions between the aromatic rings.

2-(N-acetylamino)pent-4-ynamide

The title compound, C 7 H 10 N 2 O 2 , displays extensive hydrogen-bonding interactions which give rise to connected 10- and 11-membered rings throughout the lattice.

Crystal structure of N2-(3-morpholinopropyl)-3-hydroxy-2-naphthamide, C18H22N2O3

Source of material: The title compound was prepared by the amidation of methyl 3-hydroxy-2-naphthalenecarbonate and 3-(4morpholinyOpropylamine in toluene under reflux (see ref. 1); the latter was prepared by the Michael addition of 4-тофЬоИпе with propenenitrile in the absence of solvent (see ref. 2) and hydrogénation of the resulting 3-(4-тофЬоипу1)ргор1от011е with Raney nickel in the ammonia saturated ethanol solution (see ref. 3). Recrystallisation was from a toluene solution; mp 416 К 417 К. The тофЬоНпе portion of the molecule lies over the naphthyl residue. This conformation is stabilised by an intramolecular Ν(14)-Η···Ν(18) interaction of 2.17 Â. A second intramolecular interaction occurs between 0(1)Η and 0(13) of 1.65 Â.

Crystal structure of 2-(N-acetyl)-5-phenylpent-4-ynamide, C13H14N2O2

Source of material: Prepared from the palladium catalysed coupling of 2-(yV-acetyl)pent-4-ynamide with iodobenzene in piperidine (see ref. 1). Recrystallised from an acetonitrile solution of the compound, mp 445 К 446 К. Two independent molecules comprise the asymmetric unit, labelled a and b, with only nriinor conformational differences between them; identical numbering schemes were employed. Signiñcant intermolecular Η-bonding is evident, involving all of the acidic H atoms. Thus, Nla-Hla 022a [d(A-H) 1.05 Â, ¿(H· B) 1.86 Ä, d(A -B) 2.894(4) Â and A-H B 169°], NlaHlbOlb [0.89 Â, 2.11Â, 2.961(4) Â and 160°] and N21aH21a 01b [0.94 Â, 2.07 Â, 2.946(4) Â and 155°] are found for moleculeaandNlb-Hlc ••022b [0.87 Â, 2.06 Â, 2.879(4) Â and 156°], Nlb-Hld -Ola [1.05 Â,1.95 Â, 2.965(4) Â and 160°] and N21b-H21b 01a [1.03 Â, 1.88 Â, 2.907(4) Â and 170°] are found for molecule b. These combine to give rise to a complex 3-D network.

Crystal structure of (5)-3-hydroxy-2-(methylcarboxamido)propanamide, C5H10N2O3

Source of material: Prepared from L-serine by esterification with methanol, acetylation with acetic acid and dicyclohexylcarbodiimide, and finally amidation with saturated ammonia solution in methanol (see refs. 1 and 2). Recrystallisation was from an acetonitrile solution; η φ 414 К 415 К. The structure shows that the^V-acetyl group is almost p^pendicular to the amide as the C(l)/C(2)/N(21)/C(22) torsion angle is -96.3(4)°. The conformation precludes intramolecular H-bonding, presumably to maximise intermolecular H-bonding. The lattice is coπφr ísed of layers of interconnected molecules lying approximately parallel to the ac plane. Signifícant H-bonds in this plane are: 0 ( 3 ) Η · 0 (22) 1.90(4) Â [0(3)· · ·0(22) 2.667(4) Â, О Н Н 175(4)°], N l H ( l b ) 0 ( 3 ) 2.01(4) Â [Ν·· ·0 2.908(5) Â, Ν-Η···0173(4)°], and N(21bH·· 0 (1) 1.98(4) Â [Ν···0 2.899(4) Â, Ν Η · О 171(3)°]. Connections between the layers are afforded by N l H ( l a ) 0 (22) contacts of 2.16(4) Â [Ν·· ·0 3.004(4) Â, Ν Η · · · 0 174(3)°].