Synthesis of 2,3,4-Trisubstituted 2-Cyclopentenones via Sequential Functionalization of 2-Cyclopentenone.

The synthesis of differently substituted 2,3,4-triarylcyclopent-2-en-1-ones from 2-cyclopentenone via sequential functionalization of a novel 2,4-dibromo-3-(4-methoxyphenyl) cyclopent-2-en-1-one intermediate has been developed. The process provides access to selective arylation at C-4 and C-2 with a broader substrates scope, which includes heteroaryl and alkyl substitution at C-2.

Benzoxazole Alkaloids: Occurrence, Chemistry, and Biology.

Benzoxazole alkaloids exhibit a diverse array of structures and interesting biological activities. In spite of the extensive research done on the synthesis and biology, till date there is no concise update on this class of alkaloids. This chapter summarizes the literature on benzoxazole alkaloids till March 2017, which covers their isolation, characterization, possible biosynthetic origins, biological activities, and major synthetic approaches.

Investigating the mode of action of sulfoxaflor: a fourth-generation neonicotinoid.

Background: The precise mode of action of sulfoxaflor, a new nicotinic acetylcholine receptor-modulating insecticide, is unclear. A detailed understanding of the mode of action, especially in relation to the neonicotinoids, is essential for recommending effective pest management practices.

Results: Radiolabel binding experiments using a tritiated analogue of sulfoxaflor ([(3) H]-methyl-SFX) performed on membranes from Myzus persicae demonstrate that sulfoxaflor interacts specifically with the high-affinity imidacloprid binding site present in a subpopulation of the total nAChR pool.

On the sequence of bond formation in loline alkaloid biosynthesis.

Loline alkaloids are saturated pyrrolizidines with an oxygen bridge between carbon atoms C-2 and C-7 and an amino group on C-1. They are bioprotective alkaloids produced by Epichloë and Neotyphodium species, mutualistic fungal endophytes that are symbiotic with cool-season grasses. The sequence of bond formation in loline alkaloid biosynthesis was determined by synthesizing deuterated forms of potential intermediates and feeding them to cultures of the endophyte Neotyphodium uncinatum.

Biosynthetic precursors of fungal pyrrolizidines, the loline alkaloids.

Loline alkaloids are saturated pyrrolizidines with a substituted 1-amino group and an oxygen bridge between C2 and C7, and are insecticidal metabolites of plant-symbiotic fungi (endophytes). Cultures of the endophyte, Neotyphodium uncinatum, incorporated labeled L-proline and L-homoserine into the 1-aminopyrrolizidine, N-formylloline. The A-ring carbons C1-C3 and the N1 were derived from L-homoserine; the B-ring carbons C5-C8 and the ring nitrogen were derived from L-proline.

Rutheniun-catalyzed cycloisomerization of o-(ethynyl)phenylalkenes to diene derivatives via skeletal rearrangement.

Treatment of a series of 2',2'-disubstituted (o-ethynyl)styrenes with TpRu(PPh(3))(CH(3)CN)(2)PF(6) (10 mol %) in benzene (80 degrees C, 12-18 h) efficiently gave 2-alkenyl-1H-indene derivatives. This catalytic reaction represents an atypical enyne cycloisomerization with skeletal rearrangement of starting enyne, where the C=C bond is completely cleaved and inserted by the terminal alkynyl carbon. The reaction mechanism was elucidated by a series of deuterium and (13)C labeling experiments, as well as by changing the substituents at the phenyl moieties.

Ruthenium-catalyzed aromatization of aromatic enynes via the 1,2-migration of halo and aryl groups: a new process involving electrocyclization and skeletal rearrangement.

The halo and aryl substituents of the 1,2-disubstituted styryl group of aromatic enynes undergo a 1,2-shift in the aromatization reaction catalyzed by TpRuPPh3(CH3CN)2PF6 (10 mol %) in toluene (110 degrees C, 6-8 h). The aryl group shifts to the neighboring olefin carbon, and the iodo (or bromo) substituent migrates to the terminal alkyne carbon. The mechanisms of these two migrations have been elucidated by isotope labeling experiments.