Bimanes (1,5‐diazabicyclo[3.3.0]octadienediones): Laser activity in syn‐bimanes
Authors: Lau Chun M. , Thangaraj Kannappan , Kumar Govindarajulu , Ramakrishnan Vayalakkavoor T. , Stevens Edwin D. , Boyer Joseph H. , Politzer Ieva R. , Pavlopoulos Theodore G. 
Published: January 2005

The conversion of 3‐methyl‐4‐benzyl‐4‐chloro‐2‐pyrazolin‐5‐one 10b was catalyzed by a mixture of potassium fluoride and alumina to give syn‐(methyl, benzyl)bimane 6 (62%) without detectable formation of the anti isomer,A6 [a 1 : 1 mixture (87%) of the isomers 6 and A6 was obtained when the catalyst was potassium carbonate]. In a similar reaction syn‐(methyl,carboethoxymethyl)bimane 7 (15%) with the anti isomer A7 (36%) was obtained from 3‐methyl‐4‐carboethoxymethyl‐4‐chloro‐2‐pyrazolin‐5‐one 10c. syn‐(Methyl, β‐acetoxyethyl)bimane 8 (70%) was obtained from 3‐methyl‐4‐β‐acetoxyethyl‐4‐chloro‐2‐pyrazolin‐5‐one 10d (potassium carbonate catalysis) and was converted by hydrolysis to syn‐(methyl, β‐hydroxyethyl)bimane 9 (40%). Acetyl nitrate (nitric acid in acetic anhydride) converted anti‐(amino,hydrogen)bimane 11 to anti‐(amino,nitro)bimane 15 (91%), anti‐(methyl,hydrogen)bimane 13 to anti‐(methyl,nitro)(methyl,hydrogen)bimane 16 (57%), and degraded syn‐(methyl,hydrogen)bimane 12 to an intractable mixture. Treatment with trimethyl phosphite converted syn‐(bromomethyl,methyl)bimane 17 to syn‐(dimethoxyphosphinylmethyl,methyl)bimane 18 (78%) that was further converted to syn‐(styryl,methyl)bimane 19 (29%) in a condensation reaction with benzaldehyde. Treatment with acryloyl chloride converted syn‐(hydroxymethyl,methyl)bimane 20 to its acrylate ester 21 (22%). Stoichiometric bromination of syn‐(methyl,methyl)bimane 1 gave a monobromo derivative that was converted in situ by treatment with potassium acetate to syn‐(acetoxymethyl,methyl)(methyl,methyl)bimane 47. N‐Amino‐μ‐amino‐syn‐(methylene,methyl)bimane 24 (68%) was obtained from a reaction between the dibromide 17 and hydrazine. Derivatives of the hydrazine 24 included a perchlorate salt and a hydrazone 25 derived from acetone. Dehydrogenation of syn‐(tetramethylene)bimane 26 by treatment with dichlorodicyanobenzoquinone (DDQ) gave syn‐(benzo,tetramethylene)bimane 27 (58%) and syn‐(benzo)bimane 28 (29%). Bromination of the bimane 26 gave a dibromide 29 (92%) that was also converted by treatment with DDQ to syn‐(benzo)bimane 28. Treatment with palladium (10%) on charcoal dehydrogenated 5, 6, 10, 11‐tetrahydro‐7H,9H‐benz [6, 7] indazol [1, 2a]benz[g]indazol‐7,9‐dione 35 to syn‐(α‐naphtho)bimane 36 (71%). The bimane 35 was prepared from 1,2,3,4‐tetrahydro‐1‐oxo‐2‐naphthoate 37 by stepwise treatment with hydrazine to give 1,2,4,5‐tetrahydro‐3H‐benz[g]indazol‐3‐one 38, followed by chlorine to give 3a‐chloro‐2,3a,4,5‐tetrahydro‐3H‐benz[g]indazol‐3‐one 39, and base. Dehydrogenation over palladium converted the indazolone 34 to 1H‐benz[g] indazol‐3‐ol 36. Helicity for the hexacyclic syn‐(α‐naphtho)bimane 36 was confirmed by an analysis based on molecular modeling.

The relative efficiencies (RE) for laser activity in the spectral region 500–530 nm were obtained for 37 syn‐bimanes by reference to coumarin 30 (RE 100): RE > 80 for syn‐bimanes 3, 5, 18, and μ‐(dicarbomethoxy)methylene‐syn‐(methylene,methyl)bimane 22: RE 20–80: for syn‐bimanes 1,2,4,20,24,26, and μ‐thia‐syn‐(methylene,methyl)bimane 50: and RE 0‐20 for 26 syn‐bimanes. The bimane dyes tended to be more photostable and more water‐soluble than coumarin 30. The diphosphonate 18 in dioxane showed laser activity at 438 nm and in water at 514 nm. Presumably helicity, that was demonstrated by molecular modeling, brought about a low fluorescence intensity for syn‐(α‐naphtho)bimane 36, Φ0.1, considerably lower than obtained for syn‐(benzo)bimane 28, Φ0.9.