Bevan, Thomas W. published the artcileA colorful azulene-based protecting group for carboxylic acids, SDS of cas: 35661-58-6, the publication is Tetrahedron (2018), 74(24), 2942-2955, database is CAplus.
An intensely blue-colored protecting group for carboxylic acids has been developed. The protecting group is introduced through Steglich esterification that couples 6-(2-hydroxyethyl)azulene (AzulE) and the carboxylic acid substrate RC(O)OH (R = cyclohexyl, (E,E)-CH3CH=CH-CH=CH, ([(9H-fluoren-9-ylmethoxy)carbonyl]amino)methyl, etc.). Deprotection is effected under basic conditions by the addition of the amidine base DBU, whereupon cleavage occurs, accompanied by a color change. A two-step deprotection methodol. comprising activation with oxalyl chloride and deprotection with a very mild base was developed for use with base-sensitive substrates. The AzulE esters I were found to be compatible with other commonly employed protecting groups – silyl ethers, MOM acetals – by studying their orthogonal and concomitant deprotections. The stability of the new protecting group towards various synthetic processes – oxidation, reduction, cross-coupling, olefination and treatment with base – provided the basis of a versatility profile. This indicated that AzulE esters are sensitive to strongly oxidizing and basic agents while being compatible with reducing conditions and selected other reactions. The convenience of a highly colored protecting group for tracking material (and avoiding loss of compound) through laboratory processes warrants further investigation of this and/or related species.
Tetrahedron published new progress about 35661-58-6. 35661-58-6 belongs to piperidines, auxiliary class Piperidine,Benzene, name is 1-((9H-Fluoren-9-yl)methyl)piperidine, and the molecular formula is C19H21N, SDS of cas: 35661-58-6.
Referemce:
https://en.wikipedia.org/wiki/Piperidine,
Piperidine | C5H11N – PubChem