Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable-temperature continuous-flow LED-photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α-Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α-aminonitriles. Primary α-aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at -50 °C. This atom-economic and protecting-group-free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert-leucine hydrochloride from neopentylamine.

Aerobic amine oxidation is an attractive and elegant process for the α functionalization of amines. However, there are still several mechanistic uncertainties, particularly the factors governing the regioselectivity of the oxidation of asymmetric secondary amines and the oxidation rates of mixed primary amines. Herein, it is reported that singlet-oxygen-mediated oxidation of 1° and 2° amines is sensitive to the strength of the α-C-H bond and steric factors. Estimation of the relative bond dissociation energy by natural bond order analysis or by means of one-bond C-H coupling constants allowed the regioselectivity of secondary amine oxidations to be explained and predicted. In addition, the findings were utilized to synthesize highly regioselective substrates and perform selective amine cross-couplings to produce imines.

An effective total synthesis of (-)-9-deoxy-englerin (4), an analogue of the natural guaiane sesquiterpene englerin A (1), has been achieved. The synthesis features a transannular epoxide opening to construct the 5,7-fused ring system followed by transannular ether formation with mercury(II) trifluoroacetate.

A cyclic carbonyl ylide with a trans-annulated cyclopentane ring was generated by a Rh(2)(OAc)(4)-catalyzed reaction from a diazoketone precursor and trapped with allyl propiolate. The 1,3-dipolar cycloaddition led to the stereoselective formation of an oxygen-bridged polycycle. Via Curtius degradation, the cycloadduct was transformed to the ring skeleton typical of the sesquiterpene family of guaianolides.

Fluorinated α‐amino acids are versatile compounds that are used for many purposes in medicinal and biochemistry. However, their synthesis remains a significant hurdle, often requiring multiple steps, multiple protecting groups, and/or the use of highly toxic reagents. These challenges have limited the application of fluorinated α‐amino acids. A convenient, protecting‐group‐free and semi‐continuous process for the synthesis of racemic fluorinated α‐amino acids from fluorinated amines is described. Following a singlet‐oxygen‐driven photooxidative cyanation, an acid‐mediated hydrolysis of the intermediate α‐amino nitrile yields the desired α‐amino acid. Aliphatic, benzylic, and homobenzylic residues with different fluorination degrees are tolerated, providing good overall yields (50–67 %). This semi‐continuous process is particularly advantageous for an aliphatic amine, the intermediate α‐amino nitrile of which decomposes upon isolation.

Tri- or tetrasubstituted α-cyanoepoxides can be rapidly prepared from unactivated amines and malononitrile or methyl cyanoacetate when singlet oxygen, produced in a continuous-flow photoreactor, serves as an oxidant and in situ peroxide source. The hydrogen peroxide generated in amine oxidation epoxidizes an electron deficient olefin intermediate, formed by deaminative Mannich coupling. The corresponding α,α-dicyano- or α-cyano-α-esterepoxides were obtained in good yields (43-82%).

Primäre und sekundäre Amine kçnnen mit Singulettsauerstoff schnell und quantitativ zu den entsprechenden Iminen oxidiert werden. Ein temperierbarer, LED-betriebener Durchflussphotoreaktor produziert in Gegenwart katalytischer Mengen Tetraphenylporphyrin als Sensibilisator die reaktive Form des Sauerstoffs. a-Aminonitrile konnten mit Trimethylsilylcyanid als In-situ-Abfangreagens in guten bis ausgezeichneten Ausbeuten hergestellt werden. Primäre Amine reagierten bei 25 8C aufgrund oxidativer Kupplung vor der Cyanidaddition zu den sekundären a-Aminonitrilen. Überraschenderweise konnten erstmals primäre a-Aminonitrile synthetisiert werden, indem die oxidative Strecker-Reaktion bei À50 8C durchgeführt wurde. Dieser Prozess kann zur atomçkonomischen und schutzgruppenfreien Herstellung racemischer Aminosäuren genutzt werden, was am Beispiel der Synthese von tert-Leucinhydrochlorid aus Neopentylamin gezeigt wird.

Reported is a safe, rapid method for the synthesis of α-nitro esters via the trapping of nitronium ions. The two-stage nitration and subsequent deacetylation of readily available 1,3-dicarbonyl compounds was achieved using a biphasic semicontinuous approach. α-Nitro esters and amides were obtained in good overall yields (53-84%). Some of the α-nitro-1,3-dicarbonyl intermediates exhibit enhanced reactivity and undergo an acid-catalyzed Nef-type reaction to α-oxo-carbonyls.