Chromoselective access to Z- or E- allylated amines and heterocycles by a photocatalytic allylation reaction

The most useful strategies for the alkylation of allylic systems are related to the Tsuji–Trost reaction or the use of different Lewis acids. Herein we report a photocatalytic approach for the allylation reaction of a variety of nucleophiles, such as heteroarenes, amines and alcohols. This method is compatible with a large variety of pyrroles and indoles, containing different substituents such as electron-withdrawing and electron-donating groups, unprotected nitrogen atoms and bromo derivatives. Moreover, this methodology enables the chromoselective synthesis of Z- or E-allylated compounds. While the use of UV-light irradiation has allowed the synthesis of the previously inaccessible Z-allylated products, E-isomers are prepared simply by changing both the light source to the visible region, and the catalytic system. Based on mechanistic and photochemical proofs, laser flash photolysis studies and DFT calculations, a rational mechanism is presented.

The mixture was then stirred at room temperature for 6 h. The reaction was quenched with water (3 mL) and extracted with DCM (3 x 10 mL). The combined organic phases were dried over MgSO 4 and the solvent evaporated under reduced pressure. The crude was used in the next step without further purification.
Procedure B for chalcone reduction: To a stirred solution of the corresponding chalcone (3.5 mmol) and CeCl 3 (106 mg, 4.2 mmol) in MeOH (15 mL) at 0 ºC, NaBH 4 (161 mg, 4.2 mmol) was added portionwise. The mixture was then stirred at room temperature for 30 min. The reaction was quenched with water (15 mL) and extracted with DCM (3 x 20 mL). The combined organic phases were dried over MgSO 4 and the solvent evaporated under reduced pressure. The crude was used in the next step without further purification.
Spectroscopic data are in agreement with the published data. 9
Spectroscopic data are in agreement with the published data. 12
The mixture was extracted with DCM (3 x 5 mL). The combined organic phases were washed with 1M HCl (8 mL), dried over MgSO 4 and the solvent evaporated under reduced pressure. The crude was used in the next step without further purification.

S22
The C2-allylated compound was obtained as a side-product:

General procedure for the preparation of Z-allylic compounds (9)
A vial equipped with a magnetic stir bar and fitted with a teflon screw cap septum was

General procedure for the preparation of E-allylic compounds (10)
A vial equipped with a magnetic stir bar and fitted with a teflon screw cap septum was charged with the corresponding allylic compound 1 (0.1 mmol), the corresponding amine or alcohol (0.2 mmol), 3-(4-methoxyphenyl)-10-phenyl-10H-phenoxazine (1.7 mg, 5 mol%) and acetonitrile (1 mL). The reaction was degassed with three freeze-pump-thaw cycles. The vial was then backfilled with N 2 and stirred under 420 nm LEDs irradiation (18.3396 W/m 2 intensity; approximate distance was 2 cm from the vial) at room temperature. After 3 h the vial was opened, the solvent evaporated and the crude purified by column chromatography.

Supplementary Notes 3:
Absorption spectrum of 1a, 3e and 3g: The absorption spectrum of a solution of the different compounds in CH 3 CN was measured using a quartz cuvette with 1 cm of optical pathway.

Determination of the reduction redox potential of the excited photocatalyst (E*red) and Rhem-Weller equation:
The reduction redox potential of the excited photocatalyst (3e and 3g) was subsequently determined. Indeed, knowing the electrochemical oxidation peak potential and

Determination of the Quantum Yield
A solution of ferrioxalate was chosen as actinometer following the procedure described by the IUPAC (subcommittee on photochemistry). 35 The procedure is based on the decomposition under irradiation of ferric ions to ferrous ions which are complexed by 1,10-phenanthroline. This photochemical transformation has a known quantum yield and the complexation of Fe 2+ with 1,10-phenanthroline can be monitored by UV-Visible absorption since its extinction coefficient at 510 nm is known ( =11100 M -1 cm -1 ).
Therefore, the moles transformed can be related with the moles of photons absorbed by the Supplementary Equation 4.

Supplementary Equation 4
The complete procedure should be done under a red safe-light environment. At 420 nm ferroxilate has a Φ = 1.05. 36   , /

Supplementary Equation 6
Where Φ () is the quantum yield of the actinometer reaction at the irradiated wavelength, in this case being 1.05 at 420 nm for 0.15 M dilution 35  isomer, and after relaxation its affords either the E-or the Z-1a in the ground state.
However, the conformation of the Z-1a triplet excited state a does not change significantly compared to the ground state, therefore after relaxation its affords Z-1a exclusively. Therefore, under UV-light irradiation, there is an accumulation of the Z-1a isomer that cannot isomerize to the E isomer, and can only undergo the photoredox reaction.
Moreover, theoretical calculations show that the SOMO orbital either in the E or in the Z allylic acetate is centered in the double bond and the phenyl ring (Supplementary Figure   25C), confirming that the injection takes place in this part of the molecule. Here we attach the images to clear out the explanation.

Theoretical evaluation of reaction between carbocation and pyrrole:
Once the formation of a common carbocation intermediate is achieved, a Friedel-Crafts reaction between the carbocation and pyrrole takes place. Theoretical calculations S60 allowed to evaluate the thermodynamics and kinetics of such process. The first required step is the approaching of the reactants to generate an initial Van der Waals complex.
The energetic difference between the initial complex and reactants calculated separately allows an estimation of the entropic cost of such approaching. In that case value of this cost is around 6 kcal/mol. From this initial complex, the system only has to overcome a