**4. Experimental**

General Information. NMR spectra were recorded in CDCl3 solutions on a Bruker DPX 300 and DPX 400 spectrometers for 1H- and 13C-NMR. Chemical shifts are reported in parts per million (ppm) relative to TMS as an internal standard. IR spectra were recorded on a JASCO FT/IR-230 spectrometer. HPLC analyses were performed on a JASCO HPLC system (JASCO PU-1580 pump, DG-1580-53, LG-2080-02, MD-2015, UV-2075 and CD-2095 detector). Single crystal X-ray structure analysis was conducted using a SMART APEX II (Bruker AXS) and APEX II ULTRA (Bruker AXS). Powder X-ray crystallographic analysis was performed using D8 ADVANCE (BRUKER AXS). Commercially available *N*-phenylmaleimide and 2-methylfuran were used without further purification. Other maleimides **2b–j** were provided according to the reported procedure [70,71]. (Figures S18–S35)

## Synthesis of Exo-**3a–j**.

The corresponding maleimides **2** (1.0 g) and 2-methylfuran **1** (15 equiv) were added to 10 mL of hexane, and the mixture was stirred at 60 ◦C for 24 h. Thereafter, the solvent and extra amount of methylfuran were removed under reduced pressure, and the crude crystalline products were recrystallized from chloroform/hexane to isolate *exo*-**3**. The structures of known adducts **3a** were determined by comparing their spectral data to literature values. The adducts, **3e–g**, and **3j** are commercially available; however, these materials were easily obtained by the above method.

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-4-Methyl-2-phenyl-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3a**) [41]

Colorless prism; 96% yield; mp: 144–146 ◦C; 1H NMR (CDCl3) δ 1.80 (s, 3H), 2.88 (d, *J* = 6.6 Hz, 1H), 3.14 (d, *J* = 6.3 Hz, 1H), 5.32, (d, *J* = 1.5 Hz, 1H), 6.38 (d, *J* = 5.7 Hz, 1H), 6.57 (dd, *J* = 1.5 and 5.4 Hz, 1H), 7.27–7.30 (m, 2H), 7.37–7.51 (m,3H); 13C NMR (CDCl3) δ 15.7, 49.5, 50.6, 81.1, 88.6, 126.5, 128.7, 129.1, 131.7, 137.1, 140.7, 174.0, 175.3. (Figures S36 and S37) The enantiomeric purity of the solid was determined by HPLC using a CHIRALPAK IA (Daicel Ind.); column. *t*R(1) = 20 min for (+)-**3a**, *t*R(2) = 30.5 min for (–)-**3a**. Eluent: hexane/EtOH = 80:20 (v/v); flow rate: 0.7 mL/min.

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(4-Chlorophenyl)-4-methyl-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*) dione (*exo*-**3b**)

Colorless crystal; m.p. 120 ◦C; 90% yield; 1H NMR (CDCl3) δ 1.78 (s, 3H), 2.85 (d, *J* = 6.5 Hz, 1H), 3.11 (d, *J* = 6.5 Hz, 1H), 5.29 (d, *J* = 1.8 Hz, 1H), 6.37 (d, *J* = 5.6 Hz, 1H), 6.55 (dd, *J* = 5.6, 1.6 Hz, 1H), 7.23–7.26 (m, 2H), 7.42–7.44 (m, 2H); 13C NMR (CDCl3) δ 15.7, 49.5, 50.6, 81.1, 88.6, 127.7, 129.2, 130.2, 134.4, 137.0, 140.7, 173.7, 175.0; IR (cm<sup>−</sup>1, KBr) 1701; HRMS (ESI-MS) *m*/*z* calcd for C15H12ClNO3 + H 290.0578, found 290.0577. (Figures S38 and S39) The enantiomeric purity of the solid was determined by HPLC using a CHIRALPAK IA (Daicel Ind.); column. *t*R(1) = 20 min for (+)-**3b**, *t*R(2) = 22 min for (–)-**3b**. Eluent: hexane/EtOH = 90: 10 (v/v); flow rate: 1.0 mL/min. (Figures S12 and S13)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(3,4-Dimethylphenyl)-4-methyl-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3 (2*H*)-dione (*exo*-**3c**)

Colorless crystal; m.p. 140 ◦C; 91% yield; 1H NMR (CDCl3) δ 1.78 (s,3H), 2.27 (s, 3H), 2.27 (s, 3H), 2.84 (d, *J* = 6.5 Hz, 1H), 3.10 (d, *J* = 6.5 Hz, 1H), 5.30 (d, *J* = 1.6 Hz, 1H), 6.36 (d, *J* = 5.6 Hz, 1H), 6.54 (dd, *J* = 5.6, 1.6 Hz, 1H), 6.96–7.01 (m, 2H), 7.21–7.26 (m, 1H); 13C NMR (CDCl3) δ 15.7, 19.5, 19.8, 49.4, 50.6, 81.0, 88.5, 123.9, 127.5, 129.2, 130.2, 137.0, 137.6, 137.7, 140.7, 174.2, 175.6; IR (cm−1, KBr) 1708; HRMS (ESI-MS) *m*/*z* calcd for C17H17NO3 + H 284.1281, found 284.1276. (Figures S40 and S41) The enantiomeric purity of the solid was determined by HPLC using a CHIRALPAK IA (Daicel Ind.); column. *t*R(1) = 29.5 min for (+)-**3c**, *t*R(2) = 33 min for (–)-**3c**. Eluent: hexane/EtOH = 80: 20 (v/v); flow rate: 0.5 mL/min. (Figures S14 and S15)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(3,5-Dichlorophenyl)-4-methyl-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3 (2*H*)-dione (*exo*-**3d**)

Colorless crystal; m.p. 136 ◦C; 99% yield; 1H NMR (CDCl3) δ 1.79 (s, 3H), 2.87 (d, *J* = 6.5 Hz, 1H), 3.13 (d, *J* = 6.5 Hz, 1H), 5.30 (d, *J* = 1.8 Hz, 1H), 6.38 (d, *J* = 5.6 Hz, 1H), 6.57 (dd, *J* = 5.6, 1.6 Hz, 1H), 7.26 (m, 2H), 7.39–7.40 (m, 1H); 13C NMR (CDCl3) δ 15.7, 49.5, 50.6, 81.2, 88.7, 125.1, 128.8, 133.3, 135.2, 137.1, 140.7, 173.2, 174.5; IR (cm<sup>−</sup>1, KBr) 1712. (Figures S42 and S43) The enantiomeric purity of the solid was determined by HPLC using a CHIRALPAK IA (Daicel Ind.); column. *t*R(1) = 13.5 min for (+)-**3d**, *t*R(2) = 16 min for (–)-**3d**. Eluent: hexane/EtOH = 90 : 10 (v/v); flow rate: 1.0 mL/min. (Figures S16 and S17)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-4-Methyl-2-(4-tolyl)-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3e**)

Colorless crystal; m.p. 132 ◦C; 90% yield; 1H NMR (CDCl3) δ 1.79 (s, 3H), 2.38 (s, 3H), 2.86 (d, *J* = 6.6 Hz, 1H), 3.12 (d, *J* = 6.6 Hz, 1H), 5.31 (d, *J* = 1.8 Hz, 1H), 6.37 (d, *J* = 5.5 Hz, 1H), 6.56 (dd, *J* = 5.6, 1.7 Hz, 1H), 7.13–7.28 (m, 4H); 13C NMR (CDCl3) δ 15.7, 21.2, 49.4, 50.6, 81.0, 88.5, 126.3, 129.1, 129.7, 137.0, 138.7, 140.7, 174.1, 175.4; IR (cm<sup>−</sup>1, KBr) 1707. (Figures S44 and S45)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(4-Fluorophenyl)-4-methyl-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*) dione (*exo*-**3f**)

Colorless crystal; m.p. 133 ◦C; 88% yield; 1H NMR (CDCl3) δ 1.78 (s, 3H), 2.86 (d, *J* = 6.5 Hz, 1H), 3.11 (d, *J* = 6.5 Hz, 1H), 5.29 (d, *J* = 1.8 Hz, 1H), 6.37 (d, *J* = 5.6 Hz, 1H), 6.55 (dd, *J* = 5.7, 1.7 Hz, 1H), 7.13–7.29 (m, 4H); 13C NMR (CDCl3) δ 15.7, 49.4, 50.6, 81.1, 88.6, 116.0, 116.2, 127.6, 128.3, 128.4, 137.0, 140.7, 160.9, 163.4, 173.9, 175.2. (Figures S46 and S47)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(4-Bromophenyl)-4-methyl-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*) dione (*exo*-**3g**)

Colorless crystal; m.p. 127 ◦C; 94% yield; 1H NMR (CDCl3) δ 1.78 (s, 3H), 2.86 (d, *J* = 6.5 Hz, 1H), 3.12 (d, *J* = 6.5 Hz, 1H), 5.29 (d, *J* = 1.8 Hz, 1H), 6.37 (d, *J* = 5.6 Hz, 1H), 6.56 (dd, *J* = 5.7, 1.7 Hz, 1H), 7.18-7.20 (m, 2H), 7.58–7.60 (m, 2H); 13C NMR (CDCl3) δ 15.7, 49.5, 50.6, 81.1, 88.6, 122.5, 128.0, 130.6, 132.2, 137.0, 140.7, 173.6, 174.9; IR (cm<sup>−</sup>1, KBr) 1705. (Figures S48 and S49)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-4-Methyl-2-(3-tolyl)-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3h**)

Colorless crystal; m.p. 128 ◦C; 93% yield; 1H NMR (CDCl3) δ 1.79 (s, 3H), 2.38 (s, 3H), 2.86 (d, *J* = 6.5 Hz, 1H), 3.12 (d, *J* = 6.5 Hz, 1H), 5.31 (d, *J* = 1.6 Hz, 1H), 6.37 (d, *J* = 5.6 Hz, 1H), 6.55 (dd, *J* = 5.6, 1.6 Hz, 1H), 7.05–7.37 (m, 4H); 13C NMR (CDCl3) δ 15.7, 21.3, 49.5, 50.6, 81.1, 88.6, 123.6, 127.1, 128.9, 129.6, 131.6, 137.0, 139.2, 140.7, 174.1, 175.4; IR (cm<sup>−</sup>1, KBr) 1707; HRMS (ESI-MS) *m*/*z* calcd for C16H15NO3 - H 268.0979, found 288.0992. (Figures S50 and S51)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(4-Ethylphenyl)-4-methyl-3a,4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*) dione (*exo*-**3i**)

Colorless crystal; m.p. 114 ◦C; 88% yield; 1H NMR (CDCl3) δ 1.24 (t, *J* = 7.7 Hz, 3H), 1.79 (s, 3H), 2.67 (q, *J* = 7.6 Hz, 2H), 2.85 (d, *J* = 6.5 Hz, 1H), 3.11 (d, *J* = 6.5 Hz, 1H), 5.30 (d, *J* = 1.8 Hz, 1H), 6.36 (d, *J* = 6.5 Hz, 1H), 6.55 (dd, *J* = 5.6, 1.6 Hz, 1H), 7.16-7.30 (m, 4H); 13C NMR (CDCl3) δ 15.3, 15.7, 28.6, 49.5, 50.6, 81.1, 88.6, 126.4, 128.6, 129.3, 137.0, 140.7, 144.9, 174.2, 175.5; IR (cm<sup>−</sup>1, KBr) 1702; HRMS (ESI-MS) *m*/*z* calcd for C17H17NO3 + H 284.1281, found 284.1277. (Figures S52 and S53)

(3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(4-Methoxyphenyl)-4-methyl-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindole-1,3 (2H)-dione (*exo*-**3j**)

Colorless crystal; m.p. 120–121 ◦C; 94% yield; 1H NMR (CDCl3) δ 1.78 (s, 3H), 2.84 (d, *J* = 6.5 Hz, 1H), 3.10 (d, *J* = 6.5 Hz, 1H), 3.82 (s, 3H), 5.29 (d, *J* = 1.8 Hz, 1H), 6.36 (d, *J* = 5.7 Hz, 1H), 6.54 (dd, *J* = 5.6, 1.6 Hz, 1H), 6.94–7.26 (m, 4H); 13C NMR (CDCl3) δ 15.7, 49.4, 50.5, 55.4, 81.0, 88.5, 114.4, 124.4, 127.7, 137.0, 140.7, 159.5, 174.3, 175.5. (Figures S54 and S55)

Single crystal X-ray structure analysis of (3a*S*,4*R*,7*S*,7a*R*)-2-(4-chlorophenyl)-4-methyl-3a,4,7,7atetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3b**)

Disordered crystal of the ratio of 73:27, exhibiting (-)-CD sign at 254 nm for major isomer. Colorless prism (0.20 <sup>×</sup> 0.20 <sup>×</sup> 0.01 mm3), orthorhombic space group *P*212121, *a* = 6.5485(4) Å, *<sup>b</sup>* <sup>=</sup> 12.3747(6) Å, *c* = 16.8764(9) Å, *V* = 1367.59(13) Å3, *Z* = 4, λ (CuKα) = 1.54178 Å, ρ = 1.407 g/cm3, μ (CuKα) = 2.539 cm, 3954 reflections measured (T = 173 K, 4.430◦ < θ < 68.264◦), nb of independent data collected: 2213 nb of independent data used for refinement: 2127 in the final least-squares refinement cycles on F2, the model converged at *R*<sup>1</sup> = 0.0505, *wR*<sup>2</sup> = 0.1993 [*I* > 2σ(*I*)], *R*<sup>1</sup> = 0.0522, *wR*<sup>2</sup> = 0.1408 (all data), and GOF = 1.065, H-atom parameters constrained, absolute Flack parameter = 0.505(8). (CCDC 1985809). (Figure S1)

Single crystal X-ray structure analysis of (3a*S*,4*R*,7*S*,7a*R*)-2-(4-chlorophenyl)-4-methyl-3a,4,7,7atetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3b**)

Enantiomerically pure crystal provided by optical resolution using HPLC, exhibiting (-)-CD sign at 254 nm. Colorless prism (0.20 <sup>×</sup> 0.20 <sup>×</sup> 0.10 mm3), orthorhombic space group *P*212121, *a* = 6.5975(2) Å, *b* = 12.3565(4) Å, *c* = 16.7223(6) Å, *V* = 1363.24(8) Å3, *Z* = 4, λ (CuKα) = 1.54178 Å, ρ = 1.412 g/cm3, μ (CuKα) = 2.547 cm, 12970 reflections measured (T = 173 K, 4.449◦ < θ < 68.213◦), nb of independent data collected: 2427, nb of independent data used for refinement: 2397 in the final least-squares refinement cycles on F2, the model converged at *R*<sup>1</sup> = 0.0369, *wR*<sup>2</sup> = 0.0985 [*I* > 2σ(*I*)], *R*<sup>1</sup> = 0.0371, *wR*<sup>2</sup> = 0.0989 (all data), and GOF = 1.059, H-atom parameters constrained, absolute Flack parameter = 0.051(3). (CCDC 1985810). (Figure S2)

Single crystal X-ray structure analysis of (3a*S*,4*R*,7*S*,7a*R*)-2-(3,4-dimethylphenyl)-4-methyl-3a,4,7,7atetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3c**)

Exhibiting (-)-CD sign at 254 nm. Colorless prism (0.20 <sup>×</sup> 0.10 <sup>×</sup> 0.10 mm3), orthorhombic space group *P*212121, *a* = 7.9707(3) Å, *b* = 12.9386(5) Å, *c* = 13.7305(5) Å, *V* = 1416.02(9) Å3, *Z* = 4, λ (CuKα) = 1.54178 Å, ρ = 1.329 g/cm3, μ (CuKα) = 0.741 cm, 21885 reflections measured (T = 173 K, 4.696◦ < θ < 68.241◦), nb of independent data collected: 2593, nb of independent data used for refinement: 2576 in the final least-squares refinement cycles on F2, the model converged at *R*<sup>1</sup> = 0.0334, *wR*<sup>2</sup> = 0.0855 [*I* > 2σ(*I*)], *R*<sup>1</sup> = 0.0335, *wR*<sup>2</sup> = 0.0856 (all data), and GOF = 1.065, H-atom parameters constrained, absolute Flack parameter = 0.099(16). (CCDC 1985811). (Figure S3)

Single crystal X-ray structure analysis of (3a*S*,4*R*,7*S*,7a*R*)-2-(3,5-dichlorophenyl)-4-methyl-3a,4,7,7atetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3d**)

Disordered crystal of the ratio of 76:24, exhibiting (-)-CD sign at 254 nm for major isomer. Colorless prism (0.30 <sup>×</sup> 0.20 <sup>×</sup> 0.20 mm3), monoclinic space group *P*21, *a* = 5.4032(5) Å, *<sup>b</sup>* <sup>=</sup> 13.9697(10) Å, *c* = 9.6673(8) Å, β = 105.179(4)◦, *V* = 704.24(10) Å3, *Z* = 2, λ (CuKα) = 1.54178 Å, ρ = 1.529 g/cm3, μ (CuKα) = 4.237 cm, 2350 reflections measured (T = 173 K, 5.7024◦ < θ < 68.068◦), nb of independent data collected: 1457, nb of independent data used for refinement: 1452 in the final least-squares refinement

cycles on F2, the model converged at*R*<sup>1</sup> =0.0532, *wR*<sup>2</sup> =0.1391 [*I* >2σ(*I*)],*R*<sup>1</sup> =0.0532, *wR*<sup>2</sup> =0.1392 (all data), and GOF = 1.125, H-atom parameters constrained, absolute Flack parameter = 0.12(3). (CCDC 1985812). (Figure S4)

Single crystal X-ray structure analysis of (3a*R*,4*S*,7*R*,7a*S*)-2-(3,5-dichlorophenyl)-4-methyl-3a,4,7,7atetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-(+)-**3d**)

Enantiomerically pure crystal provided by optical resolution using HPLC. Colorless prism (0.30 <sup>×</sup> 0.20 <sup>×</sup> 0.20 mm3), monoclinic space group *P*21, *a* = 5.3713(9) Å, *b* = 13.958(2) Å, *c* = 9.5751(14) Å, β = 103.609(5)◦, *V* = 697.72(19) Å3, *Z* = 2, λ (CuKα) = 1.54178 Å, ρ = 1.529 g/cm3, μ (CuKα) = 4.277 cm, 10993 reflections measured (T = 173 K, 4.752◦ < θ < 72.198◦), nb of independent data collected: 2558, nb of independent data used for refinement: 2519 in the final least-squares refinement cycles on F2, the model converged at *R*<sup>1</sup> = 0.0429, *wR*<sup>2</sup> = 0.1034 [*I* > 2σ(*I*)], *R*<sup>1</sup> = 0.0431, *wR*<sup>2</sup> = 0.1036 (all data), and GOF = 1.101, H-atom parameters constrained, absolute Flack parameter = 0.110(5). (CCDC 1985813). (Figure S5)

Single crystal X-ray structure analysis of analysis of (3a*R*,4*S*,7*R*,7a*S*)-4-methyl-2-(4-tolyl)-3a,4,7,7atetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3e**)

Colorless prism (0.20 <sup>×</sup> 0.10 <sup>×</sup> 0.10 mm3), orthorhombic space group *P*212121, *a* = 9.3007(6) Å, *b* = 10.6635(6) Å, *c* = 13.7010(9) Å, *V* = 1358.84(15) Å3, *Z* = 4, λ (CuKα) = 1.54178 Å, ρ = 1.316 g/cm3, μ (CuKα) = 0.746 cm, 4911 reflections measured (T = 173 K, 6.314◦ < θ < 68.278◦), nb of independent data collected: 2263, nb of independent data used for refinement: 2225 in the final least-squares refinement cycles on F2, the model converged at*R*<sup>1</sup> =0.0458, *wR*<sup>2</sup> =0.1278 [*I* >2σ(*I*)],*R*<sup>1</sup> =0.0462, *wR*<sup>2</sup> =0.1284 (all data), and GOF = 1.048, H-atom parameters constrained, absolute Flack parameter = 0.39(7). (CCDC 1985814). (Figure S6)

Single crystal X-ray structure analysis of analysis of (3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(4-fluorophenyl)-4-methyl-3a, 4,7,7a-tetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3f**)

Colorless prism (0.20 <sup>×</sup> 0.10 <sup>×</sup> 0.03 mm3), monoclinic space group *P*21/c, *a* = 9.9813(13) Å, *b* = 13.0236(15) Å, *c* = 9.7580(8) Å, β = 101.379(9)◦, *V* = 1243.5(2) Å3, *Z* = 4, λ (CuKα) = 1.54178 Å, ρ = 1.460 g/cm3, μ (CuKα) = 0.945 cm, 2238 reflections measured (T = 173 K, 5.655◦ < θ < 68.328◦), nb of independent data collected: 2238, nb of independent data used for refinement: 1687 in the final least-squares refinement cycles on F2, the model converged at *R*<sup>1</sup> = 0.0687, *wR*<sup>2</sup> = 0.1787 [*I* > 2σ(*I*)], *R*<sup>1</sup> = 0.0915, *wR*<sup>2</sup> = 0.1875 (all data), and GOF = 1.172, H-atom parameters constrained. (CCDC 1985815). (Figure S7)

Single crystal X-ray structure analysis of (3a*S*\*,4*R*\*,7*S*\*,7a*R*\*)-2-(4-bromophenyl)-4-methyl-3a,4,7,7atetrahydro-1*H*-4,7-epoxyisoindole-1,3(2*H*)-dione (*exo*-**3g**).

Colorless prism (0.20 <sup>×</sup>0.20 <sup>×</sup>0.20 mm3), monoclinic space group *<sup>P</sup>*21/n, *<sup>a</sup>*=20.838(6) Å, *<sup>b</sup>* <sup>=</sup> 6.485(2) Å, *c* = 20.853(6) Å, β = 104.364(3)◦, *V* = 2729.9(15) Å3, *Z* = 8, λ (MoKα) = 0.71073 Å, ρ = 1.626 g/cm3, μ (MoKα) = 3.018 cm, 5224 reflections measured (T = 173 K, 1.593◦ < θ < 27.570◦), nb of independent data collected: 5224, nb of independent data used for refinement: 3679 in the final least-squares refinement cycles on F2, the model converged at *R*<sup>1</sup> = 0.0511, *wR*<sup>2</sup> = 0.1118 [*I* > 2σ(*I*)], *R*<sup>1</sup> = 0.0928, *wR*<sup>2</sup> = 0.1310 (all data), and GOF = 1.025, H-atom parameters constrained. (CCDC 1985818). (Figure S8)

Reaction conditions for asymmetric DA reaction via dynamic crystallization

In a sealed tube (*L* = 200 mm, Φ = 25 mm), *N*-arylmaleimide **2** (100 mg), 2-methylfuran **1** (15 eq.), TFA (0–1.0 eq), and heptane (1.0 mL) were stirred with or without glass beads (250 mg) using a stir bar at 80 ◦C. The crystalline adduct **3** appeared after a few minutes, and the solution was kept in suspension by stirring at 600 rpm for several days at 80 ◦C. The change of ee value of crystalline **3** was monitored by HPLC using CHIRALPAK IA (Daicel Ind.) column; eluent: *n*-hexane/EtOH. Finally, crystalline *exo*-**3** was isolated by filtration. The same procedure was performed for all substrates.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2073-8994/12/6/910/s1, Figure S1: Single crystal X-Ray crystallographic analysis of *exo*-**3b** (disordered), Figure S2: Single crystal X-Ray crystallographic analysis of *exo*-**3b** (enantiopure), Figure S3: Single crystal X-Ray crystallographic analysis of *exo*-**3c** (enantiopure), Figure S4: Single crystal X-Ray crystallographic analysis of *exo*-**3d** (disordered), Figure S5: Single crystal X-Ray crystallographic analysis of *exo*-**3d** (enantiopure), Figure S6: Single crystal X-Ray crystallographic analysis of *exo*-**3e** (enantiopure), Figure S7: Single crystal X-Ray crystallographic analysis of *exo*-**3f**, Figure S8: Single crystal X-Ray crystallographic analysis of *exo*-**3g**, Figure S9: Time course for DA reaction of **1** (0.5 M) and **2b–d** (0.05 M) at 60 ◦C in CDCl3 monitored by 1H NMR, Figure S10: Time course for reverse-DA reaction of *exo*-**3b–d** (0.05 M) at 60 ◦C in CDCl3 monitored by 1H NMR, Figure S11: Time course for reverse-DA reaction of *exo*-**3b–d** (0.03 M) in the presence of TFA (0.03 eq) at 60 ◦C in CDCl3 monitored by 1H NMR, Figure S12: HPLC analysis of racemic *exo*-**3b**, Figure S13: HPLC analysis of 40% ee of *exo*-(-)-**3b**, Figure S14. HPLC analysis of racemic of *exo*-**3c**, Figure S15. HPLC analysis of 98% ee of *exo*-(-)-**3c**, Figure S16. HPLC analysis of racemic of *exo*-**3d**, Figure S17. HPLC analysis of 49% ee of *exo*-(+)-**3d**, Figure S18: 1H NMR spectrum of maleimide **2b**, Figure S19: 13C NMR spectrum of maleimide **2b**, Figure S20: 1H NMR spectrum of maleimide **2c**, Figure S21: 13C NMR spectrum of maleimide **2c**, Figure S22: 1H NMR spectrum of maleimide **2d**, Figure S23: 13C NMR spectrum of maleimide **2d**, Figure S24: 1H NMR spectrum of maleimide **2e**, Figure S25: 13C NMR spectrum of maleimide **2e**, Figure S26: 1H NMR spectrum of maleimide **2f**, Figure S27: 13C NMR spectrum of maleimide **2f**, Figure S28: 1H NMR spectrum of maleimide **2g**, Figure S29: 13C NMR spectrum of maleimide **2g**, Figure S30: 1H NMR spectrum of maleimide **2h**, Figure S31: 13C NMR spectrum of maleimide **2h**, Figure S32: 1H NMR spectrum of maleimide **2i**, Figure S33: 13C NMR spectrum of maleimide **2i**, Figure S34: 1H NMR spectrum of maleimide **2j**, Figure S35: 13C NMR spectrum of maleimide **2j**, Figure S36: 1H NMR spectrum of *exo*-**3a**, Figure S37: 13C NMR spectrum of *exo*-**3a**, Figure S38: 1H NMR spectrum of *exo*-**3b**, Figure S39: 13C NMR spectrum of *exo*-**3b**, Figure S40: 1H NMR spectrum of *exo*-**3c**, Figure S41: 13C NMR spectrum of *exo*-**3c**, Figure S42: 1H NMR spectrum of *endo*-**3d**, Figure S43: 13C NMR spectrum of *endo*-**3d**, Figure S44: 1H NMR spectrum of *exo*-**3e**, Figure S45: 13C NMR spectrum of *exo*-**3e**, Figure S46: 1H NMR spectrum of *endo*-**3f**, Figure S47: 13C NMR spectrum of *endo*-**3f**, Figure S48: 1H NMR spectrum of *exo*-**3g**, Figure S49: 13C NMR spectrum of *exo*-**3g**, Figure S50: 1H NMR spectrum of *endo*-**3h**, Figure S51: 13C NMR spectrum of *endo*-**3h**, Figure S52: 1H NMR spectrum of *exo*-**3i**, Figure S53: 13C NMR spectrum of *exo*-**3i**, Figure S54: 1H NMR spectrum of *endo*-**3j**, Figure S55: 13C NMR spectrum of *endo*-**3j**.

**Author Contributions:** Conceptualization, M.S.; methodology, N.U., S.T., W.S., M.S.; validation, Y.Y. and T.M.; formal analysis, N.U., S.T., W.S.; investigation, N.U., S.T., W.S.; data curation, Y.Y., T.M., M.S.; writing—original draft preparation, N.U., S.T., M.S.; writing—review and editing, M.S.; supervision, M.S.; project administration, M.S.; funding acquisition, M.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by Grants-in-Aid for Scientific Research (No. 19H02708) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of the Japanese Government. Uemura acknowledges financial support from the Frontier Science Program of the Graduate School of Science and Engineering, Chiba University.

**Conflicts of Interest:** The authors declare no conflict of interest.
