We report the application of visible-light photoredox catalysis for the formation of C-C bonds between tertiary N-arylamines and nitroalkanes via an oxidative aza-Henry reaction. In the presence of 1 mol % Ir(ppy)(2)(dtbbpy)PF(6), efficient coupling of nitroalkanes with in situ-generated iminium ions provides the desired products in up to 96% yield. Mechanistic studies suggest that reductive quenching of the Ir(3+) excited state by the tertiary amine leads to the ammonium radical cation, with subsequent catalyst turnover (Ir(2+) --> Ir(3+)) likely effected by atmospheric oxygen.

2.2. Chiral Imines and Imine Derivatives 2.2.1. Imines and Imine Derivatives from Chiral Carbonyl Compounds. Chiral α-oxysubstituted aldehydes were used by Kobayashi and co-workers in a three-component reaction with allylboropinacolate and ammonia in ethanol. The corresponding homoallylic primary amines were obtained with good to high syn diastereofacial selectivities (Scheme 5). 20 The precise reaction mechanism was unclear. Preformation of N-Scheme 3 Scheme 4 Scheme 5 Chemical Reviews Review dx.

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A metal-free dehydrogenative lactonization of 2-arylbenzoic acids at room temperature was developed. This work illustrates the first application of visible-light photoredox catalysis in the preparation of benzo-3,4-coumarins, an important structural motif in bioactive molecules. The combination of photocatalyst [Acr + -Mes] with (NH 4 ) 2 S 2 O 8 as terminal oxidant provides an economical and environmentally benign entry to different substituted benzocoumarins. Preliminary mechanistic studies suggest that this reaction most likely occurs through a homolytic aromatic substitution pathway.

An operationally simple method is disclosed for the decarboxylative cyanation of aliphatic carboxylic acids at room temperature. Riboflavin tetraacetate, an inexpensive organic photocatalyst, promotes the oxidation of carboxylic acids upon visiblelight activation. After decarboxylation, the generated radicals are trapped by TsCN, yielding the desired nitriles without any further additive, in a redox-neutral process. Importantly, this protocol can be adapted to flow conditions.

Abstract:We describe herein a transition-metal-free method for the decarboxylative generation of radicals from carboxylic acids and their 1,4-addition to Michael acceptors. The Fukuzumi catalyst (9-mesitylene-10-methylacridinium perchlorate, [AcrMes]ClO 4 ) enabled this transformation under visible-light irradiation at room temperature with CO 2 as the only byproduct. The scope and limitations of this protocol were examined by using

ABSTRACT:A stereocontrolled general methodology to access all natural tetraponerines from (+)−T1 to (+)−T8 is detailed. Two consecutive indium-mediated aminoallylations with the appropriate enantiomer of chiral N-tert-butylsulfinamide and a thermodynamic control at the aminal stereocenter, allow the formation of each natural tetraponerine with excellent stereoselectivity. The use of 4-bromobutanal in the first aminoallylation leads to the formation of 5-6-5 tetraponerines whilst 5-bromopentanal is required to build the scaffold of 6-6-5 tetraponerines. A cross-metathesis reaction of the second aminoallylation product with cis-3-hexene is used to elongate the side chain up to 5 carbons so as to prepare the tetraponerines T5 to T8. The anticancer activity of these heavier tetraponerines against four different carcinoma human cell lines is examined, observing a promising cytotoxic activity of (+)−T7 against breast carcinoma cell line MCF-7.

The combination of an aldehyde, an allylic bromide, and tert-butanesulfinamide in the presence of indium metal and titanium tetraethoxide allows straightforward access to homoallylamine derivatives in high yields and stereoselectivities. Moreover, the synthetic utility of the enantioenriched homoallylamine derived from n-decanal was illustrated in a concise synthesis of (+)-isosolenopsin. In this context, similar homoallylamines has been recently used by other groups in the synthesis of naturally occurring alkaloids.