Studies on the Intramolecular Cycloaddition Reaction of Mesoionics Derived from the Rhodium(II)-Catalyzed Cyclization of Diazoimides
摘要:
A series of alkenyl-substituted imides were prepared by treating the appropriate amide with 2,2,6-trimethyl-4H-1,3-dioxen-4-one in xylene at 140-degrees-C to give the N-acetoacylated imides. Exposure of these imides to standard diazo transfer conditions gave the desired diazoimides. The carbenoid intermediate derived by treatment of the diazoimide with rhodium(II) acetate undergoes ready cyclization onto the neighboring amide carbonyl oxygen atom to generate an isomunchnone intermediate. Subsequent 1,3-dipolar cycloaddition across the pendant olefin affords the cycloadduct in high yield. The stereochemical assignment of several of the cycloadducts was deduced by X-ray crystallography. The stereochemical outcome of the reaction is the consequence of an endo cycloaddition of the neighboring pi-bond across the transient isomunchnone dipole. Molecular mechanics calculations were used to model energy differences between the endo and exo diastereomers. The calculations reveal that the endo diastereomers are significantly (8-12 kcal/mol) lower in energy than the corresponding exo isomers thereby providing a rationale for the preferred endo cycloaddition. Ring opening of the cycloadducts occurred readily producing a transient N-acyliminium ion which either lost a proton to give an enamide or was reduced by Et3SiH to afford a bicyclic piperidine ring.
A pesticidal composition comprises at least one compounds selected from a compound of formula, or any agriculturally acceptable salt thereof, wherein R
1
, R
2
, R
3
, R
4
, R
5
, R
6,
R
7
, R
8
, Q, Z, L, L
a
, and x are as described herein. A method of controlling pests comprises applying the pesticidal composition near a population of pests.
One-Pot Synthesis of Five-, Six-, and Seven-Membered Lactams via Bu<sub>3</sub>SnH-Mediated Reductive Cyclization of Azido Amides
作者:Su-Jeong Lee、In-Jung Heo、Chang-Woo Cho
DOI:10.5012/bkcs.2012.33.2.739
日期:2012.2.20
involves the use of triphenylphosphines and water toafford various γ- and δ-lactams in good to excellent yields.Owing to the importance of lactams in natural products andpharmaceuticals, the development of new and diverse routesfor efficient, single-step lactamsynthesis from azido amideswith expanded substrate scope is highly desirable. There-fore, we planned to develop another methodology for thedirect
A pesticidal composition comprises at least one compounds selected from a compound of formula, or any agriculturally acceptable salt thereof, wherein R1, R2, R3, R4, R5, R6, R7, R8, Q, Z, L, La, and x are as described herein. A method of controlling pests comprises applying the pesticidal composition near a population of pests.