Photoirradiation of 3-alkoxy-6-chloro-2-(2'-furyl) -4-0x0-4H-1 -benzopyrans 3 led to the formation of methyl 8-chloro-1 O-oxo-2-phenyl-2,3,4,1 O-tetrahydropyrano[3,2-b] [l 3 benzopyran-3-ylacetate 4.The reaction proceeds through the formation of 8-chlor0-4-phenyl-3a,4,6,11 b-tetrahydrofuro-[2'.3':4,5]pyrano[3.2-b] benzopyran-6-one 5a, which subsequently undergoes a ring contraction-ring expansion mechanism to give the cyclopropanecarbaldehyde 8 followed by its rearrangement to ketene 10 via the carbene 9 to furnish ester 4. The various intermediates have been isolated and identified, and their stereochemistry was established from their 'H NMR spectra.Conjugated enones with suitable substituents at the a-position, when subjected to photolysis, are known to undergo y-H abstractions.' The products obtained depend invariably upon the nature of the substituents present in the substrates: viz. 2alkyl-3-arylcyclohex-2-enones and 3-alkoxy-2-phenyl-4-oxo-4H-1 -benzopyrans afforded photocyclised angular products whereas 3-benzyloxy-2-styrylchromones,4 upon exposure to W light, yielded tricyclic linear products. In contrast 3methoxy-2-methylchromone has been found to lead to the formation of a novel dimeric oxetanol.' It thus became of interest to investigate the photochemistry of 3-alkoxychromones bearing a fury1 group instead of a Me, Ph or CH=CHPh at C(2), since furans themselves are known to undergo phototransformations.6 Such a system allows another dimension, here, to be studied as it becomes a bichromophoric system, an enone coupled to a furan. Results and DiscussionThe target molecules, i.e., 2-(2'-furyl)-3a ' and 2-(5'-methyl-2'furyl)-3-benzyloxy-4-oxo-4H-1 -benzopyran 3b were synthesised as follows (Scheme 1).Photoirradiation of 3a in methanol produced ester 4, whose structure became evident from its 'H NMR and mass spectra. The 'H NMR spectrum (100 MHz) of compound 4 showed a

β-Diketiminato copper(I) complexes play important roles in bioinspired catalytic chemistry and in applications to the materials industry. However, it has been observed that these complexes are very susceptible to disproportionation. Coordinating solvents or Lewis bases are typically used to prevent disproportionation and to block the coordination sites of the copper(I) center from further decomposition. Here, we incorporate this coordination protection directly into the molecule in order to increase the stability and reactivity of these complexes and to discover new copper(I) binding motifs. Here we describe the synthesis, structural characterization, and reactivity of a series of unsymmetrical N-aryl-N'-alkylpyridyl β-diketiminato copper(I) complexes and discuss the structures and reactivity of these complexes with respect to the length of the pyridyl arm. All of the aforementioned unsymmetrical ß-diketiminato copper(I) complexes bind CO reversibly and are stable to disproportionation. The binding ability of CO and the rate of pyridyl ligand decoordination of these copper(I) complexes are directly related to the competition between the degree of puckering of the chelate system and the steric demands of the N-aryl substituent.

The β-diketiminato copper(II) L1CuCl−L4CuCl and their nitrite complexes L1Cu(O2N) and L2Cu(O2N) has been synthesized and characterized. The X-ray structure of the L1CuCl−L4CuCl complexes clearly indicates towards the mononuclear structure with...

The synthesis of unsymmetrical β‐diketimines with N‐aryl‐N′‐alkyl substitution require at least two condensation steps and tedious purification procedures. An improvement in the preparation of four unsymmetrical N‐aryl‐N′‐alkylpyridyl β‐diketimine ligands (HL1–HL4) using 5‐Å molecular sieves is reported. The synthesis of four Li complexes (LiL1, LiL2, LiL3, and LiL4) containing N‐aryl‐N′‐alkylpyridyl β‐diketimines ligands is also presented. All four Li complexes were fully characterized by 1H NMR spectroscopic, 13C NMR spectroscopic, and elemental analyses. X‐ray structure analysis and spectroscopic results indicate that the Li β‐diketimine structures and ligand binding modes are governed by the bulkiness of the N‐aryl substituent and the length of the pyridyl arm of the N‐aryl‐N′‐alkyl β‐diketiminate ligand.