Nitroalkane

Abstract: The Curtius rearrangement is a classic, powerful method for converting carboxylic acids into protected amines, but its widespread use is impeded by safety issues (the need to handle azides). We have developed an alternative to the Curtius rearrangement that employs a copper catalyst in combination with blue-LED irradiation to achieve the decarboxylative coupling of aliphatic carboxylic acid derivatives (specifically, readily available N-hydroxyphthalimide esters) to afford protected amines under mild conditions. This C–N bond-forming process is compatible with a wide array of functional groups, including an alcohol, aldehyde, epoxide, indole, nitroalkane, and sulfide. Control reactions and mechanistic studies are consistent with the hypothesis that copper species are engaged in both the photochemistry and the key bond-forming step, which occurs through out-of-cage coupling of an alkyl radical.

Abstract: The cyclic urea DMPU (N, N′-dimethyl-N, N′-propylene urea = 1,3-dimethyl-2-oxo-hexahydropyrimidine) is shown to exhibit the same effects HMPT in oxirane-opening with Li-acetylide, in a Wittig olefination, in the double deprotonation of nitroalkane, in the Michael addition of Li-dithiane to cyclohexenone, and in selective generations of certain enolates (Schemes 1–7) DMPU might therefore be as safe substitute of the carcinogenic HMPT as a cosolvent with unique properties in diverse type of reaction.

Abstract: Synthetic control over chirality and function is the crowning achievement for metal-organic frameworks, but the same level of control has not been achieved for covalent organic frameworks (COFs). Here we demonstrate chiral COFs (CCOFs) can be crystallized from achiral organic precursors by chiral catalytic induction. A total of nine two-dimensional CCOFs are solvothermally prepared by imine condensations of the C3-symmetric 1,3,5-triformylphloroglucinol (Tp) with diamine or triamine linkers in the presence of catalytic amount of (R)- or (S)-1-phenylethylamine. Homochirality of these CCOFs results from chiral catalyst-induced immobilization of threefold-symmetric tris(N-salicylideneamine) cores with a propeller-like conformation of one single handedness during crystallization. The CCOF-TpTab showed high enantioselectivity toward chiral carbohydrates in fluorescence quenching and, after postsynthetic modification of enaminone groups located in chiral channels with Cu(II) ions, it can also be utilized as a heterogeneous catalyst for the asymmetric Henry reaction of nitroalkane with aldehydes.

Abstract: In order to facilitate interpretation of the deazaisoalloxazine system as a valid mechanistic probe of flavoenzyme catalysis, we have examined some of the fundamental chemical properties of this system The enzymatic synthesis, on a micromole scale, of the flavin coenzyme analogues 5-deazariboflavin 5'-phosphate (deazaFMN) and 5-deazariboflavin 5'-diphosphate, 5' leads to 5'adenosine ester (deazaFAD) has been achieved This latter synthesis is accomplished with a partially purified FAD synthetase complex (from Brevibacterium ammoniagenes), containing both phosphorylating and adenylylating activities, allowing direct conversion of the riboflavin analogue to the flavin adenine dinucleotide level The structure of the reduced deazaflavin resulting from enzymatic and chemical reduction is established as the 1,5-dihydrodeazaflavin by proton magnetic resonance Similarly, the C-5 position of the deazaflavins is demonstrated to be the locus for hydrogen transfer in deazaflavin redox reactions Preparation of 1,5-dihydrodeazaflavins by sodium borohydride reduction stabilized them to autoxidation (t 1/2 approximately 40 h, 22 degrees C) although dihydrodeazaflavins are rapidly oxidized by other electron acceptors, including riboflavin, phenazine methosulfate, methylene blue, and dichlorophenolindophenol Mixtures of oxidized and reduced deazaflavins undergo a rapid two-electron disproportionation (k = 22 M-1 S-1 0 degrees C), and oxidized deazaflavins form transient covalent adducts with nitroalkane anions at pH less than 5 Generalized methods for the synthesis of isotopically labeled flavin and deazaflavin coenzymes and their purification by adsorptive chromatography are given