N- vs O-Coordination in cyclomanganation of 1,5-diaryl-3-(2-pyridyl)pentane-1,5-diones and 3-(2-pyridyl)chalcones; cyclomanganation at saturated carbon and the crystal structure of [1,5-diphenyl-κC2-3-(2-pyridyl- κN)pentan-2-yl-κC2-1,5-dione-κO1κO5]tetracarbonylmanganesetricarbonylmanganese
作者:Warren Tully、Lyndsay Main、Brian K. Nicholson
DOI:10.1016/j.jorganchem.2005.04.016
日期:2005.7
Reaction of 1,5-diphenyl-3-(2-pyridyl)pentane-1,5-dione (5a) with 2.5 moles of benzylpentacarbonylmanganese in petroleum spirit under reflux gives a small amount of the symmetric di-aryl-manganated product [1,5-diphenyl-kappa C-2-3-(2-pyridyl)pentane-1,5-dione-kappa O(1)kappa O-5]bis-(tetracarbonylmanganese) (7a), but mostly [1,5-diphenyl-kappa C-2-3-(2-pyridyl-kappa N)pentan-2-yl-kappa C-2-1,5-dione-kappa O(1)kappa O-5]tetracarbonylmanganesetricarbonylmanganese (6a) which is manganated at only one aryl carbon [by Mn(CO)4] but also [by Mn(CO)3 with N and O coordination] at the methylene carbon adjacent to the Mn(CO)(4)-coordinated ketone carbonyl. The latter is a rare example of direct cyclomanganation at a saturated carbon and the only known case adjacent to a carbonyl group; the X-ray crystal structure of 6a is reported. With 3 moles of benzylpentacarbonylmanganese the yield of 6a remains unchanged but some trimanganation product [1, 5-diphenyl-kappa C(2')kappa C-2'''-3-(2-pyridyl-kappa N)pentan-2-yl-kappa C-2-1,5-dione-kappa O(1)kappa O-5]tris-(tetracarbonylmanganese) (8a) is formed, presumably from 7a. Routes to products are proposed and activating factors considered. 1,5-Di-(2-thienyl)-3-(2-pyridyl)pentane-1,5-dione (5b) and its 3-thienyl isomer (5c) similarly give 6a analogues [1,5-di-(2-thienyl-kappa C-3)-3-(2-pyridyl-kappa N)pentan-2-yl-kappa C-2-1, 5-dione-kappa O(1)kappa O-5]tetracarbonylmanganesetricarbonylmanganese (6b) and [1,5-di-(3-thienyl-kappa C-2)-3-(2-pyridyl-kappa N)pentan-2-yl-kappa C-2-1,5-dione-kappa O(1)kappa O-5]tetracarbonylmanganesetricarbonylmanganese (6c).Also reported are the mono-cyclomanganation product [1-(2,6-dimethoxyphenyl)-3-(2-pyridyl-kappa N)prop-2-en-2-yl-kappa C-1-one]tetracarbonylmanganese (16) and dicyclomanganation product [1-(2,5-dimethyl-3-thienyl-kappa C-4)-3-(2-pyridyl-kappa N)prop-2-en-2-yl-kappa C-2-1-one-kappa O]bis-(tetracarbonylmanganese) (17) from reaction of the respective (E)-1-aryl-3-(2-pyridyl)prop-2-en-1-ones(3-(2-pyridyl)chalcones), the first reported examples of enone metallation at the alpha-carbon via N-coordination by a beta-2-pyridyl group. (c) 2005 Elsevier B.V. All rights reserved.