Anti-Markovnikov Hydroazidation of Activated Olefins via Organic Photoredox Catalysis

Abstract

Organic azides serve as synthetically useful surrogates for primary amines, a functional group which is ubiquitous in bioactive and medicinally relevant molecules. Historically, the formal hydroazidation of simple activated olefins and styrenes has proven difficult due to the inherent propensity of these compounds to oligomerize. Herein is disclosed a method for the anti-Markovnikov hydroazidation of activated olefins, catalyzed by an organic acridinium salt under irradiation from blue LEDs. This method is applicable to a variety of substituted and terminal styrenes and several vinyl ethers, yielding synthetically versatile hydroazidation products in moderate to excellent yield.

Improved Synthesis Strategy for N‐Methoxy‐1,3‐oxazinane Nucleic Acids (MOANAs)

“…Synthesis of the 4‐(benzoyloxy)benzylidene protected (2 R ,3 S )‐4‐(methoxyamino)butane‐1,2,3‐triol phosphoramidite building block 2 is outlined in Scheme 3. (2 R ,3 S )‐4‐(methoxyamino)butane‐1,2,3‐triol [33] ( 1 ) was first allowed to react with 4‐(benzoyloxy)benzaldehyde [41] under acidic conditions to afford a mixture of the desired N ‐methoxy‐1,3‐oxazinane 3 as well as the respective oxazolidine product, resulting from ring closure by O3 rather than O2 (Scheme 1). The primary hydroxy group of 3 was protected as a dimethoxytrityl ether, giving intermediate 4 , and the remaining secondary hydroxy group phosphitylated by conventional methods to afford the phosphoramidite building block 2 .…”

Alkyl Enol Ethers: Development in Intermolecular Organic Transformation

“…The catalyst 198 excited by 465 LED light and involve in the photoinduce electron transfer to enol ether, then nucleophilic addition of azide with a cation‐radical intermediate of enol ether and produce azide‐enol ether radical adduct which transforms into the final product 197 by hydrogen atom transfer (HAT) with 2,4,6‐triisopropylthiophenol (TRIP‐SH) (Scheme 62). [94] …”

Visible-Light-Enabled Ortho-Selective Aminopyridylation of Alkenes with N-Aminopyridinium Ylides

“…We reasoned that the use of open-shell radical cation species from either an N -aminopyridinium ylide or alkene would provide an energetic driving force and enable a stepwise 1,3-dipolar cycloaddition. To explore such a strategy, we considered two different approaches to radical-mediated 1,3-dipolar cycloaddition: (1) single-electron-transfer (SET) oxidation of alkenes to generate electrophilic alkene radical cations , that react with nucleophilic N -aminopyridinium ylides and (2) photocatalytic generation of N -radical pyridinium salts to enable radical addition to the C–C π-systems of alkenes. The strategy of the photocatalytic alkene carboamination through alkene radical cation intermediates has provided efficient synthetic access to structurally diverse amine derivatives. , Although remarkable advances have been realized, this approach restricts the alkene scope because the oxidation potentials of some common unactivated alkenes (i.e., terminal aliphatic olefins) prohibitively exceed the redox potentials of even highly oxidizing excited-state photocatalysts as illustrated in Figure .…”