A new method for the synthesis of chiral diene rhodium catalysts is introduced. The readily available racemic tetrafluoro-benzobarrelene complexes [(R 2 -TFB)RhCl] 2 were separated into two enantiomers via selective coordination of one of them with the auxiliary S -salicyl-oxazoline ligand. One of the resulting chiral complexes with an exceptionally bulky diene ligand [( R,R -iPr 2 -TFB)RhCl] 2 proved to be an efficient catalyst for the asymmetric insertion of diazoesters into B-H and Si-H bonds giving the functionalized organoboranes and silanes with high yields (79-97%) and enantiomeric purity (87-98% ee). The stereoselectivity of separation via auxiliary ligand and that of the catalytic reaction was predicted by DFT calculations.
https://ift.tt/34HtLNH
A practical synthesis of SF5Cl from sulfur powder, dry KF, and trichloroisocyanuric acid (TCCA) in MeCN is described. The new synthetic utility of SF5Cl is well demonstrated by the chemoselective hydro(chloro)pentafluorosulfanylation of diazo compounds.
Abstract
Pentafluorosulfanyl chloride (SF5Cl) is the most prevalent reagent for the incorporation of SF5 group into organic compounds. However, the preparation of SF5Cl often relies on hazardous reagents and specialized apparatus. Herein, we described a safe and practical synthesis of a bench-stable and easy-to-handle solution of SF5Cl in n-hexane under gas-reagent-free conditions. The synthetic application of SF5Cl was demonstrated through the unprecedented reaction with diazo compounds. The chemoselective hydro- and chloropentafluorosulfanylations of α-diazo carbonyl compounds were developed in the presence of K3PO4 or copper catalyst, respectively. These reactions provide a direct and efficient access to various α-pentafluorosulfanyl carbonyl compounds of high value for potential applications.
https://ift.tt/330lrYG
Trimethylsilylium abstraction from a cobalt nitrilimide complex generates a transient cobalt diazomethanediide complex, which forms a terminal isocyanoamido ligand through a radical de‐arylation.
Abstract
Lithium trimethylsilyldiazomethanide and a cobalt (II) precursor with an N‐anchored tris‐NHC (TIMENmes) ligand provide access to the cobalt nitrilimide 1. Complex 1 was structurally characterized by single‐crystal X‐ray diffractometry (SC‐XRD) and its electronic structure was examined in detail, including EPR spectroscopy, SQUID magnetometry and computational analyses. The desilylation of the C‐(trimethylsilyl)nitrilimide reveals a transient complex with an elusive diazomethanediide ligand, which substitutes one of the mesitylene rings of the ancillary ligand through C−N bond cleavage. This transformation results in the cyclometalated cobalt(II) complex 2, featuring a rare isocyanoamido‐κ‐C ligand.
https://ift.tt/3dTkir7
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c01483
María Álvarez, Maria Besora, Francisco Molina, Feliu Maseras, Tomás R. Belderrain, and Pedro J. Pérez
https://ift.tt/39bFwyX
The complete biosynthetic pathway of alazopeptin, the tripeptide consisting of two molecules of DON (6‐diazo‐5‐oxo‐l‐norleucine) and one alanine, is revealed. The heterologous production of N‐acetyl‐DON in Streptomyces albus was also established. Most interestingly, the transmembrane protein AzpL was indicated to catalyze diazotization using 5‐oxolysine and nitrous acid as substrates.
Abstract
DON (6‐diazo‐5‐oxo‐l‐norleucine), a diazo‐containing amino acid, has been studied for more than 60 years as a potent antitumor agent, but its biosynthesis has not been elucidated. Here we reveal the complete biosynthetic pathway of alazopeptin, the tripeptide Ala‐DON‐DON, which has antitumor activity, by gene inactivation and in vitro analysis of recombinant enzymes. We also established heterologous production of N‐acetyl‐DON in Streptomyces albus. DON is synthesized from lysine by three enzymes and converted to alazopeptin by five enzymes and one carrier protein. Most interestingly, transmembrane protein AzpL was indicated to catalyze diazotization using 5‐oxolysine and nitrous acid as substrates. Site‐directed mutagenesis of AzpL indicated that the hydroxy group of Tyr‐93 is important for the diazotization. These findings expand our knowledge of the enzymology of N−N bond formation.
https://ift.tt/31gllLz
A radically new approach to the synthesis of 1‐(dialkylamino)‐1,2,3‐triazoles via addition of diazomethyl radicals to hydrazones is described. This reactivity confirms the utility of the α‐diazosulfonium salts herein introduced as synthetic equivalents of the diazomethyl cation.
Abstract
The one‐pot synthesis of a series of sulfonium salts containing transferable diazomethyl groups is described, and the structure of these compounds is elucidated by X‐ray crystallography. Under photochemical conditions, reaction of these salts with N,N‐dialkyl hydrazones affords 1‐(dialkylamino)‐1,2,3‐triazoles via diazomethyl radical addition to the azomethine carbon followed by intramolecular ring closure. The straightforward transformation of the structures thus obtained into mesoionic carbene–metal complexes is also reported and the donor properties of these new ligands characterized.
https://ift.tt/2WDVnPV
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c12683
Fei Tan, Maoping Pu, Jun He, Jinzhao Li, Jian Yang, Shunxi Dong, Xiaohua Liu, Yun-Dong Wu, and Xiaoming Feng
https://ift.tt/2M5me61
A major challenge in the field of RNA chemistry is the identification of selective and quantitative conversion reactions on RNA that can be used for tagging and any other RNA tool development. Here, we introduce metal‐free diazotransfer on native RNA containing an aliphatic primary amino group using the diazotizing reagent fluorosulfuryl azide (FSO 2 N 3 ). The reaction provides the corresponding azide‐modified RNA in nearly quantitatively yields without affecting the nucleobase amino groups. The obtained azido‐RNA can then be further processed utilizing well‐established bioorthogonal reactions such as azide‐alkyne cycloadditions (Click) or Staudinger ligations. We exemplify the robustness of this approach for the synthesis of peptidyl‐tRNA mimics and for the pull‐down of acp 3 U and k 2 C containing tRNAs of the E.coli tRNA pool isolated from cellular extracts. Our approach therefore adds a new dimension to the targeted chemical manipulation of diverse RNA species.
https://ift.tt/357x55B
2 Become 1 : Lewis acidic boranes are employed in the metal‐free alkenylation reactions of aryl esters with α‐diazoesters to give highly functionalized alkene, enyne, and diene products in good to excellent yields. DFT studies have elucidated the mechanism for the reaction.
Abstract
Herein we report a facile, mild reaction protocol to form carbon–carbon bonds in the absence of transition metal catalysts. We demonstrate the metal‐free alkenylation reactions of aryl esters with α‐diazoesters to give highly functionalized enyne products. Catalytic amounts of tris(pentafluorophenyl)borane (10–20 mol %) are employed to afford the C=C coupled products (31 examples) in good to excellent yields (36–87 %). DFT studies were used to elucidate the mechanism for this alkenylation reaction.
https://ift.tt/2yXGgZo
A transition‐metal‐free C(sp 2 )‐C(sp 2 ) bond formation reaction via the cross‐coupling of diazo quinones with catechol boronic esters was developed. With this protocol, a variety of biaryls and alkenyl phenols were obtained in good to high yields under mild conditions. The reaction tolerates various functionalities and is applicable to the derivatization of pharmaceuticals and natural products. The synthetic utility of the method was demonstrated by the short synthesis of multi‐substituted triphenylenes and three bioactive natural products, honokiol, moracin M and stemofuran A. Mechanistic studies and density functional theory (DFT) calculations revealed that the reaction involves attack of the boronic ester by a singlet quinone carbene followed by a 1,2‐rearrangement via a stepwise mechanism.
https://ift.tt/2UUCZ4V
Cyclobutanones are synthetically versatile compounds that often requires extensive effort to access. Herein, we report a facile synthesis of cyclobutanones based on the C(sp 3 )‐H insertion chemistry of oxidatively generated gold carbenes. A range of cyclobutanones was obtained in synthetically useful yields from substrates with minimal structural prefunctionalization. This discovery reveals new synthetic utilities of gold‐catalyzed oxidative transformations of alkynones.
https://ift.tt/3dzApI5
Despite the growing importance of volatile functionalized diazoalkanes in organic synthesis, their safe generation and utilization remain a formidable challenge due to their difficult handling along with storage and security issues. In this study, we developed a bench‐stable difluoroacetaldehyde N ‐triftosylhydrazone (DFHZ‐Tfs) as an operationally safe diazo surrogate that can in situ release two low‐molecular‐weight diazoalkanes, diazoacetaldehyde (CHOCHN 2 ) or difluorodiazoethane (CF 2 HCHN 2 ), in a controlled fashion under specific conditions. DFHZ‐Tfs has been successfully employed in the Fe‐catalyzed cyclopropanation and Doyle–Kirmse reactions, thus highlighting the synthetic utility of DFHZ‐Tfs in the efficient construction of molecule frameworks containing CHO or CF 2 H groups. Moreover, the reaction mechanism for the generation of CHOCHN 2 from CF 2 HCHN 2 was elucidated by density functional theory (DFT) calculations.
https://ift.tt/2vsPjiP
Chain growth: A copper‐catalyzed one‐pot C1‐to‐C3 process enables the conversion of α‐diazo esters into 1,1‐bis(trifluoromethyl)alkenes using TMSCF3 as the sole fluorocarbon source. The reaction proceeds at room temperature and is scalable.
Abstract
A Cu‐catalyzed gem‐bis(trifluoromethyl)olefination of α‐diazo esters, using TMSCF3 as the only fluorocarbon source, has been developed and provides an exquisite method to access gem‐bis(trifluoromethyl)alkenes. This unprecedented olefination process involves a carbene migratory insertion into “CuCF3” to generate the α‐CF3‐substituted organocopper species, which then undergoes β‐fluoride elimination and two consecutive addition‐elimination processes to give the desired products. The key to this efficient one‐pot C1‐to‐C3 synthetic protocol lies in the controllable double (over single and triple) trifluoromethylations of the gem‐difluoroalkene intermediates.
https://ift.tt/2Tvvjoc
Structurally complex diazo‐containing scaffolds are formed by conjugate addition to vinyl diazonium salts. The electrophile, a little studied α‐diazonium‐α,β‐unsaturated carbonyl compound, is formed at low temperature under mild conditions by treating β‐hydroxy‐α‐diazo carbonyls with Sc(OTf) 3 . Conjugate addition occurs selectively at the 3‐position of indole to give α‐diazo‐β‐indole carbonyls, and enoxy silanes react to give 2‐diazo‐1,4‐dicarbonyl products. These reactions result in the formation of tertiary and quaternary centers, and give products that would be otherwise difficult to form. Importantly, the diazo functional group is retained within the molecule for future manipulation. Treating a α‐diazo ester indole addition product with Rh2(OAc)4 caused a rearrangement to occur to give a 2‐(1 H ‐indol‐3‐yl)‐2‐enoate. In the case of diazo ketone compounds, this shift occurred spontaneously on prolonged exposure to the Lewis acidic reaction conditions.
https://ift.tt/2L0hgTF
The site‐selective “cut and sew” transformations employing diazo compounds and hypervalent iodine(III) compounds involve the departure of leaving groups, a “cut” process, followed by reorganizing of fragments by bond connections, a “sew” process. Bearing controllable “cutting” sites, diazo compounds and hypervalent iodine(III) compounds hold a critical role as versatile reagents in a wide range of organic transformations, because their excellent nucleofugal ability allows for a large number of unusual reactions to occur. In recent years, the concept of combining diazo compounds and hypervalent iodine(III) reagents has emerged as a promising tool for developing new and valuable approaches, and has achieved considerable success. In this Minireview, the combination concept is systemically illustrated with recent advances in this field, with the aim of elaborating the synthetic utilities and potentials of this concept as a powerful strategy in organic synthesis.
https://ift.tt/3dXf6k5
Played with screen printing about 2 years ago, and I bought some emulsion and activated it via Diazo. It's been in my fridge for a little over 2 years. is it still good? or do I have to buy another container?
Thank you in advance.
Hi, I'm very new to screen printing and just purchased some speedball diazo emulsion and when mixing the sanitizer paste it didn't mix into the water completely and now there is small black chunks in the emulsion.
Is this something I have done wrong? I filled it half way with distilled water and shook it for ages in a dark room before mixing it.
So what I really want to know is if there is a way I can fix this or do I need to buy a new emulsion kit?
Pentafluorosulfanyl chloride (SF 5 Cl) is the most prevalent reagent for the incorporation of SF 5 group into organic compounds. However, the preparation of SF 5 Cl often relied on hazardous reagents and specialized apparatuses. Herein we described a safe and practical synthesis of a bench‐stable and easy‐to‐handle solution of SF 5 Cl in n ‐hexane under gas‐reagent‐free conditions. The synthetic application of SF 5 Cl was demonstrated through the unprecedented reaction with diazo compounds. The chemoselective hydro‐ and chloropentafluorosulfanylations of α‐diazo carbonyl compounds were developed in the presence of K 3 PO 4 or copper catalyst respectively. These reactions provide a direct and efficient access to various α‐pentafluorosulfanyl carbonyl compounds of high value for potential applications.
https://ift.tt/330lrYG
Lithium trimethylsilyldiazomethanide and a cobalt (II) precursor with an N ‐anchored tris −NHC (TIMEN mes ) ligand provide access to the cobalt nitrilimide 1 . Complex 1 was structurally characterized by single‐crystal X‐ray diffractometry (SC‐XRD) and its electronic structure was examined in detail, including EPR spectroscopy, SQUID magnetometry and computational analyses. The desilylation of the C ‐(trimethylsilyl)nitrilimide reveals a transient complex with an elusive diazomethanediide ligand, which substitutes one of the mesitylene rings of the ancillary ligand through C–N bond cleavage. This transformation results in the cyclometalated cobalt(II) complex 2 , featuring a rare isocyanoamido‐κ‐C ligand.
https://ift.tt/2YX7EQN
The one pot synthesis of a series of sulfonium salts containing transferable diazomethyl groups is described, and the structure of these compounds elucidated by X‐ray crystallography. Under photochemical conditions, reaction of these salts with N,N‐dialkyl hydrazones affords 1‐(dialkylamino)‐1,2,3‐triazoles via diazomethyl radical addition to the azomethine carbon followed by intramolecular ring closure. The straightforward transformation of the structures thus obtained into mesoionic carbene‐metal complexes is also reported and the donor properties of these new ligands characterized.
https://ift.tt/2WDVnPV
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c05183
https://ift.tt/312YJOl
Herein we report a facile, mild reaction protocol to form carbon‐carbon bonds in the absence of transition metal catalysts. We demonstrate the metal‐free alkenylation reactions of aryl esters with α‐diazoesters to give highly functionalized enyne products. Catalytic amounts of tris(pentafluorophenyl)borane (10–20 mol%) are employed to afford the C=C coupled products (31 examples) in good to excellent yields (36–87%). DFT studies have been undertaken to elucidate the mechanism for this alkenylation reaction.
https://ift.tt/2yXGgZo
