Cyclization of 1,6-diyne and 1,6-enyne with Aromatic Linkage Induced by Ruthenium Complex
Date Issued
2011
Date
2011
Author(s)
Lin, Chin-Ti
Abstract
We studied the chemical reactions of Cp(PPh3)2RuCl with 1,6-endiyne compound 1N in which one of the triple bonds is propagylic alcohol. At first, reaction of 1N with ruthenium complex generates phosphonium acetylide complex 2 in high yield. Modification of different functional groups at Cgamma led to different tendencies of cyclizations. In order to modify saturated alkyl functional groups at Cgamma, complex 2 was treated with vinyl and isopropenyl Grignard reagents to form 4a and 4b. Subsequent desiylation produces 5a and 5b with terminal alkynyl hydrogen. Cyclization between Cbeta and terminal alkynyl carbon generated a six-membered ring cyclic vinylidene via 6-endo-dig pathway. Cyclic vinylidene complexes 6a and 6b were characterized by 1H, 31P, 13C, COSY, HSQC, HMBC spectra and mass analyses.
Treatment of 2 in the presence of K2CO3 in alcohols yielded alkoxy substituted acetylide complexes 7a and 7b. Surprisingly, cyclization of acetylide complexes 7a and 7b each with a methoxy group revealed different pathways of C-C bond formation. To better understand the controlling factors, further alternative experiments showed that the solvent plays a key role in regioselective cyclizations of 10a and 8a. For 10a and 8a, we assume the aprotic-protic intrinsic property of solvent dominates the cyclization pathways, which are 6-endo-dig and 5-exo-dig. In addition, a similar reaction of 2 in EtOH also worked, which generated 8b and 10b. However, the regioselectivity to form vinylidene complex 10b with a five-membered ring via 5-exo-dig pathway from 7b is lower. Furthermore, cyclic vinylidene 10a and 10b are able to undergo transformation via carbyne to form the acyl complex 9 in slightly basic condition. In opposite, 8a transforms via 1,3 alkoxy shift to form methoxy carbene in chlorofom.
We also studied reactivity of the acetylide complex obtained from 1,6-enyne 1. Treatment of 1 with Cp(PPh3)2RuCl in the presence of KPF6 in MeOH afforded the vinylidene complex 12. Deprotonation of 12, carried out with NaOMe in MeOH, was leading to the acetylide complex 13. Cyclization of 13 occurs between Cbeta and the vinyl carbon to form a cyclic vinylidene 14. The structure was characterized by 1H, 31P, 13C, HMBC spectra and mass analyses.
Subjects
diyne
acetylide
ruthenium
allenylidene
vinylidene
cyclization
Type
thesis
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