169701-01-3

Upstream product

• 100-52-7 benzaldehyde 
• 114622-49-0 6-tert-butylazulene 
• 542-92-7 cyclopenta-1,3-diene 
• 3978-81-2 4-tert-butylpyridine 
• 154678-35-0 6-tert-butyl-1-azulenemonocarbaldehyde 
• 255839-40-8 6,6'-di-t-butyl-3,3'-benzylidenedi(1-azulenecarbaldehyde) 

Relevant academic research and scientific papers

Decarbonylation reaction of 1-azulenecarbaldehydes under mild conditions. A strategy for the protection of 1- and/or 3-position of azulene rings

The reaction of 1-azulenecarbaldehydes 9a and b with pyrrole (8) in acetic acid resulted in decarbonylation to afford azulenes even at room temperature in 49 and 78% yields, respectively. 1,3-Azulenedicarbaldehydes also reacted with 8 to give azulenes in 36 and 52% yields, respectively. This decarbonylation reaction was adopted to the selective synthesis of 3,3'- unsubstituted di(1-azulenyl)methane derivatives 7a-d. Acid-catalyzed condensation of 9a and b with paraformaldehyde or benzaldehyde afforded 3,3'- methylenedi(1-azulenecarbaldehyde)s, following this decarbonylation reaction gave the desired 7a-d as a sole product in 33-59% yields starting from 9a and b. Such decarbonylation is because of the ability of protonation of azulene ring in acidic condition and because of electron-donating properties of pyrrole ring. This reaction would serve as a new strategy for the protection of 1- and/or 3-positions of azulene ring.

Syntheses of Azulene Analogues of Triphenylmethyl Cation: Extremely Stable Hydrocarbon Carbocations and the First Example of a One-Ring Flip as the Threshold Rotation Mechanism for Molecular Propellers

A series of azulene analogues of triphenylmethyl cation (tri(1-azulenyl)methyl, di(1-azulenyl)phenylmethyl, and (1-azulenyl)diphenylmethyl hexafluorophosphates) were synthesized by hydride abstraction from the corresponding methane derivatives with DDQ.In order to examine the effect of substituents on the cations, and to enhance their stabilities, a series of cations bearing 3-methyl, 3-methoxycarbonyl, 3,6-di-t-butyl, or 3-t-butyl, 6-t-butyl groups on each of the azulene rings were also synthesized.Their pKR+ values showed that the stabilities of these cations dramatically increase with the number of azulene rings.Tris(3,6-di-t-butyl-1-azulenyl)methyl cation showed the highest pKR+ value (14.3) ever observed.The high stabilities of these cations were attributed to a large conjugative effect between the central cation and the azulene ring(s).The dynamic stereochemistry of these cations was also studied based on the temperature-dependent 1H NMR spectra, which were analyzed by a flip mechanism.Low-temperature NMR studies indicated that tri(1-azulenyl)methyl cations exist in two types of propeller conformations (symmetrical and unsymmetrical propellers, which have C3(A) and C1(B) symmetries, respectively), and at higher temperature the NMR reflect the rapid isomerization.The lower ativation energy of the process B->(or->A), compared with that of B->, indicates that the threshold rotation mechanism for the cation is a one-ring flip.This is the first example of a molecular propeller with a threshold rotation mechanism comprising a one-ring flip.