Organocatalytic Remote Stereocontrolled 1,8-Additions of Thiazolones

12 hours ago - A remote stereocontrolled 1,8-conjugate addition of thiazolones to propargylic aza-p-quinone methides formed from propargylic alcohols ...
1 downloads 0 Views 954KB Size
Download PDF
Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX

pubs.acs.org/OrgLett

Organocatalytic Remote Stereocontrolled 1,8-Additions of Thiazolones to Propargylic Aza‑p‑quinone Methides Lili Zhang,†,§ Yuzhe Han,‡,§ Anqi Huang,† Pei Zhang,† Pengfei Li,*,‡ and Wenjun Li*,† †

Department of Medicinal Chemistry, School of Pharmacy, Qingdao University, Qingdao 266021, P. R. China Department of Chemistry and Shenzhen Key Laboratory of Marine Archaea Geo-Omics, Southern University of Science and Technology, Shenzhen 518055, P. R. China

‡

Downloaded via NOTTINGHAM TRENT UNIV on September 5, 2019 at 20:59:14 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: A remote stereocontrolled 1,8-conjugate addition of thiazolones to propargylic aza-p-quinone methides formed from propargylic alcohols has been developed with the aid of a chiral phosphoric acid, and this represents the first report on organocatalytic stereocontrolled 1,8-addition of propargylic aza-p-quinone methides. Notably, the remote stereocontrolled activation protocol enables the construction of vicinal sulfur-containing quaternary carbon stereocenters and axially chiral tetrasubstituted allenes and promotes the chemistry of chiral phosphoric acids.

O

we explore the scope of organocatalytic asymmetric 1,8conjugate additions. In spite of their importance,12 aza-quinone methides (azaQMs) have received far less attention than their QMs analogues. Notably, the established organocatalytic methodologies almost exclusively focus on the asymmetric 1,4additions of aza-o-QMs.13 The only one example in the field of remote stereocontrolled conjugate addition of aza-p-QMs was reported by Sun et al. in 2017 (Scheme 1C).14 Actually, besides the ubiquitous difficulties in organocatalytic remote stereocontrolled additions, the undesired electron-rich dienamine system of aza-p-QMs might present additional challenges in terms of the reactivity and selectivity. As a result, aza-p-QMs have not been involved in the 1,8-additions. Herein, we report an asymmetric 1,8-conjugate addition of propargylic aza-p-QMs catalyzed by CPA, which would be the first example of 1,8-conjugate addition of aza-p-QMs, furnishing a series of 1,8-adducts possessing adjacent axially chiral tetrasubstituted allenes and sulfur-containing quaternary stereocenters (Scheme 1D). We initiated our studies by evaluating the reaction between propargylic alcohol 1a and 5-methyl-2-phenylthiazol-4(5H)one 2a in dichloromethane at room temperature in the presence of chiral phosphoric acids (Table 1). Encouragingly, the CPA-1-catalyzed reaction proceeded smoothly to furnish the desired 1,8-adduct 3aa in 91% yield, albeit with 4% ee (Table 1, entry 1). Of particular note are the absolute regioselectivity and excellent diastereoselectivity. After the screening of CPAs, it was found that CPA-5 was more suitable

rganocatalytic remote stereocontrol is an attractive strategy for the construction of stereocenters at certain positions far from reactive functional groups but overcomes the formidable challenge of controlling both the regiochemistry and the stereochemistry in the reaction of prochiral nucleophiles with electron-deficient conjugate systems.1 In this respect, the organocatalytic asymmetric 1,6-conjugate addition reactions have been paid much attention.2 In particular, impressive results have been achieved with respect to organocatalytic enantioselective 1,6-additions of p-quinone methides (p-QMs).3 Although the electronic effect of the directing functional group could be propagated through a conjugated π system to maintain the reactivity,4 it is wellknown that organocatalytic asymmetric 1,8-addition is more challenging,5 and this field is still in its infancy.6 The main reason might be the fact that no suitable reaction partners are found and no proper catalytic system has been established to construct the new ζ (zeta) stereocenter. Recently, Lin, Sun, and co-workers have successfully developed an organocatalytic remote stereocontrolled 1,8-conjugate addition of propargylic p-QMs with the aid of chiral N-triflylphosphoramide (Scheme 1A).7 Importantly, the synthetic strategy allows catalytic asymmetric synthesis of allene from propargylic alcohols8 and enables the formation of adjacent axially chiral allene and carbon stereocenters.9 Similarly, we also developed a chiral phosphoric acid (CPA)-catalyzed 1,8-conjugate addition of thiazolones and azlactones to p-QMs formed from propargylic alcohols, constructing adjacent axially chiral tetrasubstituted allenes and heteroatom-containing quaternary carbon stereocenters with high efficiency (Scheme 1B).10 On the basis of these results and as a continuation of our interest in developing organocatalytic remote stereocontrolled conjugate additions,11 © XXXX American Chemical Society

Received: August 2, 2019

A

DOI: 10.1021/acs.orglett.9b02726 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Table 1. Optimization of the Reaction Conditionsa

Scheme 1. Organocatalytic Remote Stereocontrolled Additions of Propargylic p-QMs and Aza-p-QMs

entry

CPA

R

solvent

yield (%)b

ee (%)c

drd

1 2 3 4 5 6 7 8 9 10 11e 12 13 14 15 16 17f 18f,g

CPA-1 CPA-2 CPA-3 CPA-4 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5 CPA-5

Me Me Me Me Me Me Me Me Me Me Me Et n-Pr i-Pr Bn Ph Ph Ph

CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CHCl3 THF PhCH3 PhCF3 PhCl PhCl PhCl PhCl PhCl PhCl PhCl PhCl PhCl

3aa, 91 3aa, 76 3aa, 89 3aa, 88 3aa, 89 3aa, 84 3aa, 46 3aa, 88 3aa, 87 3aa, 93 3aa, 89 3ab, 84 3ac, 87 3ad, 76 3ae, 92 3af, 90 3af, 87 3af, 75

4 0 14 0 20 24 6 42 18 50 50 34 48 68 66 88 96 78

>20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 3:1 2:1 3:1 1.5:1 >20:1 >20:1 >20:1

a

for affording adduct 3aa in 89% yield with 20% ee and >20:1 dr (Table 1, entry 5). Notably, an essential improvement in enantioselectivity was achieved after the investigation of reaction media (Table 1, entries 6−10). When 1-chlorobenzene (PhCl) was employed as the reaction medium, 1,8-adduct 3aa was formed in 93% yield with 50% ee and >20:1 dr (Table 1, entry 10). Decreasing the reaction temperature led to similar results (Table 1, entry 11). With the aim of further improving the enantioselectivity, we investigated the effect of the substituent (R) of the nucleophilic thiazolones 2.10,15 Pleasingly, the enantioselectivity was enhanced significantly because of the better steric discrimination (Table 1, entries 12−15). In particular, the CPA-5-catalyzed reaction of propargylic alcohol 1a and 2,5-diphenylthiazol-4(5H)-one 2f furnished the desired product 3af in 90% yield with 88% ee and >20:1 dr (Table 1, entry 16). It is worth noting that further tuning of the parameters could improve the enantioselectivity to 96% without compromising the efficiency and diastereoselectivity (Table 1, entry 17). When the catalyst loading was decreased from 5 to 2 mol %, 1,8-adduct 3af was obtained in 75% yield with 78% ee and >20:1 dr (Table 1, entry 18). With the optimal reaction conditions in hand, we then investigated the substrate scope of propargylic alcohols 1. The N-protective group of propargylic alcohols 1 was first evaluated. As shown in Table 2, the group on the nitrogen atom of propargylic alcohols 1 had a huge impact on the efficiency and stereoselectivity. The bulky adamantanecarbonyl group proved to be superior for furnishing the 1,8-adduct 3af in 87% yield with 96% ee and >20:1 dr (Table 2, entry 1). The use of N-[4-(1-hydroxy-1,3-diphenylprop-2-ynyl)phenyl]pivalamide furnished 1,8-adduct 3bf in 96% yield with 44% ee and 3:1 dr (Table 2, entry 2). The Ts-protected propargylic

Unless noted, 1a (0.05 mmol), 2 (0.06 mmol), CPA (5 mol %), solvent (0.3 mL), room temperature (rt), 24 h. bIsolated yield. c Determined by chiral-phase HPLC analysis. dDiastereomeric ratio (dr), determined by 1H NMR. eAt 0 °C, 48 h. fPhCl (1.0 mL), 36 h. g CPA-5 (2 mol %), 60 h.

Table 2. Effect of the N-Protective Group of 1a

entry

PG

yield (%)b

ee (%)c

drd

1 2 3

adamantanecarbonyl tert-butylcarbonyl 4-toluenesulfonyl (Ts)

3af, 87 3bf, 96 3cf, 94

96 44 60

>20:1 3:1 4:1

a

Unless noted, 1 (0.05 mmol), 2f (0.06 mmol), CPA-5 (5 mol %), PhCl (1.0 mL), rt, 36 h. bIsolated yield. cDetermined by chiral-phase HPLC analysis. dDiastereomeric ratio (dr), determined by 1H NMR.

alcohol 1c gave 1,8-adduct 3cf in 94% yield with 60% ee and 4:1 dr (Table 2, entry 3). Having identified the best N-protective group, we examined the substrate scope of propargylic alcohols 1 by the CPA-5catalyzed reactions of 2,5-diphenylthiazol-4(5H)-one 2f (Table 3). Notably, this methodology could be applied to various propargylic alcohols 1 bearing different types of aromatic substituents (Ar1), furnishing a series of 1,8-adducts featuring adjacent axially chiral tetrasubstituted allenes and sulfurcontaining quaternary carbon stereocenters. Importantly, both electron-withdrawing [F, Cl, and Br (Table 3, entries 1−3, 5, and 6)] and electron-donating [Me and MeO (Table B

DOI: 10.1021/acs.orglett.9b02726 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Table 3. Scope of Propargylic Alcohols 1a

Table 4. Scope of Thiazolones 2a

entry

Ar1

yield (%)b

ee (%)c

drd

entry

Ar2

yield (%)b

ee (%)c

drd

1 2 3 4 5 6 7 8

4-FC6H4 4-ClC6H4 4-BrC6H4 4-MeOC6H4 3-FC6H4 3-BrC6H4 3-MeC6H4 3-thienyl

3df, 90 3ef, 89 3ff, 81 3gf, 80 3hf, 90 3if, 80 3jf, 88 3kf, 89

92 94 96 96 88 88 90 92

>20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1

1e 2 3 4 5 6 7 8 9 10 11

4-FC6H4 4-ClC6H4 4-BrC6H4 4-MeC6H4 3-FC6H4 3-ClC6H4 3-BrC6H4 3-MeC6H4 2-FC6H4 2-naphthyl 2-thienyl

3ag, 83 3ah, 95 3ai, 89 3aj, 84 3ak, 93 3al, 95 3am, 92 3an, 96 3ao, 86 3ap, 81 3aq, 83

80 95 96 >99 98 96 90 84 86 99 90

>20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1 >20:1

a

Unless noted, 1 (0.05 mmol), 2f (0.06 mmol), CPA-5 (5 mol %), PhCl (1.0 mL), rt, 36 h. bIsolated yield. cDetermined by chiral-phase HPLC analysis. dDiastereomeric ratio (dr), determined by 1H NMR. a

Unless noted, 1a (0.05 mmol), 2 (0.06 mmol), CPA-5 (5 mol %), PhCl (1.0 mL), rt, 36 h. bIsolated yield. cDetermined by chiral-phase HPLC analysis. dDiastereomeric ratio (dr), determined by 1H NMR. e At 0 °C, 60 h.

3, entries 4 and 7, respectively)] groups were compatible and gave the corresponding 1,8-adducts 3df−jf in 80−90% yields with 88−96% ee and >20:1 dr. It should be noted that both the electronic nature and the position of the substituents on the aromatic ring of propargylic alcohols affected the yield and asymmetric induction slightly. Furthermore, heteroaromatic propargylic alcohol 1k was compatible to react smoothly with nucleophile 2f to furnish the corresponding 1,8-adduct 3kf in 89% yield with 92% ee and >20:1 dr (Table 3, entry 8). The absolute configuration of 3jf was unambiguously confirmed by X-ray crystallography.16 Confirmed by the impressive results, the organocatalytic remote stereocontrolled 1,8-additions of aza-p-QMs were established, not only furnishing the axially chiral tetrasubstituted allene unit but also simultaneously constructing vicinal sulfur-containing quaternary carbon stereocenters, which is still an important issue in asymmetric synthesis.17 Encouraged by these results, we then expanded the generality of organocatalytic remote stereocontrolled 1,8conjugate additions with regard to thiazolones 2 (Table 4). Generally, the reaction reached completion within 36 h to generate 1,8-adducts 3 in high yields without the formation of the isomeric 1,6-adducts or the 1,4-adducts. Various substituents, in terms of electron-withdrawing [F, Cl, and Br (Table 4, entries 1−3, 5−7, and 9)] and electron-donating [Me (Table 4, entries 4 and 8)] groups could be introduced into the aromatic ring of Ar2 in thiazolones 2. Obviously, the effect of these substituents on the efficiency and asymmetric induction of the reaction was not evident in terms of the electronic nature or position. Furthermore, the reaction of 2(naphthalen-2-yl)-5-phenylthiazol-4(5H)-one gave 1,8-adduct 3ap in 81% yield with 99% ee and >20:1 dr (Table 4, entry 10). In addition, the scope of the nucleophile was successfully extended to heteroaromatic thiazolone 2q, affording the corresponding 1,8-adduct 3aq in 83% yield with 90% ee and >20:1 dr (Table 4, entry 11). Altogether, these results indicated that CPA-5-catalyzed remote stereocontrolled 1,8additions of aza-p-QMs were successfully extended to a variety of thiazolones and provided robust access to diversified frameworks featuring adjacent axially chiral tetrasubstituted allenes and sulfur-containing quaternary carbon stereocenters. After fully establishing the scope of organocatalytic remote stereocontrolled 1,8-additions of aza-p-QMs, we performed

further investigations to demonstrate the utility of this methodology (Scheme 2). In the presence of CPA-5, 0.80 Scheme 2. Further Investigations

mmol of propargylic alcohol 1a reacted with thiazolone 2f smoothly to generate 1,8-adduct 3af in 88% yield with 94% ee and >20:1 dr (Scheme 2A). Upon treatment with NaBH3CN, diastereoselective reduction of 1,8-adduct 3af was achieved to generate product 4af in 97% yield with 94% ee and 15:1 dr (Scheme 2B). To gain insight into the reaction mechanism, control experiments were carried out. First, dehydration of propargylic alcohol was investigated under acidic conditions. As we expected, dehydration of propargylic alcohol 1a occurred to form aza-p-QM intermediate 1a′ in the presence of CPA-5. Via the ESI-MS spectrum, we trapped aza-p-QM intermediate 1a′ in the mixture of propargylic alcohol 1a and CPA-5, but we failed to isolate aza-p-QM 1a′ (see the Supporting Information). Furthermore, we found that propargylic alcohol 1a, aza-p-QM intermediate 1a′, and 1,8-adduct 3af coexisted in the reaction mixture of propargylic alcohol 1a, 2,5-diphenylthiazol-4(5H)-one 2f, and CPA-5 (see the Supporting Information). On this basis, the chiral phosphoric acidcatalyzed reaction between propargylic alcohol 1a and thiazolone 2f was proposed to proceed via 1,8-conjugate C

DOI: 10.1021/acs.orglett.9b02726 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters

of Shandong Province (tsqn201812047), the Natural Science Foundation of Shandong Province (ZR2017JL011), and the Shenzhen Innovation of Science and Technology Commission (JCYJ20170817110526264 and ZDSYS201802081843490).

addition (Scheme 3). Under acidic conditions, propargylic alcohol 1a generated aza-p-QM intermediate 1a′ and 2,5Scheme 3. Proposed Reaction Mechanism

■

(1) For reviews, see: (a) Csákÿ, A. G.; de la Herrán, G.; Murcia, M. C. Chem. Soc. Rev. 2010, 39, 4080. (b) Biju, A. ChemCatChem 2011, 3, 1847. (c) Silva, E. M. P.; Silva, A. M. S. Synthesis 2012, 44, 3109. (d) Jiang, H.; Albrecht, Łu.; Jørgensen, K. A. Chem. Sci. 2013, 4, 2287. (e) Lear, M. J.; Hayashi, Y. ChemCatChem 2013, 5, 3499. (f) Chauhan, P.; Kaya, U.; Enders, D. Adv. Synth. Catal. 2017, 359, 888. (g) Liu, T.; Liu, J.; He, C.; Cheng, F. Youji Huaxue 2017, 37, 2609. (2) (a) Tian, X.; Liu, Y.; Melchiorre, P. Angew. Chem., Int. Ed. 2012, 51, 6439. (b) Zhou, W.; Ni, C.; Chen, J.; Wang, D.; Tong, X. Org. Lett. 2017, 19, 1890. (c) Przydacz, A.; Kowalczyk, R.; Albrecht, Ł. Org. Biomol. Chem. 2017, 15, 9566. (d) Yoshioka, K.; Yamada, K.; Uraguchi, D.; Ooi, T. Chem. Commun. 2017, 53, 5495. (e) Gillard, R. M.; Fernando, J. E. M.; Lupton, D. W. Angew. Chem., Int. Ed. 2018, 57, 4712. (f) Uraguchi, D.; Shibazaki, R.; Tanaka, N.; Yamada, K.; Yoshioka, K.; Ooi, T. Angew. Chem., Int. Ed. 2018, 57, 4732. (g) Skrzyńska, A.; Drelich, P.; Frankowski, S.; Albrecht, Ł. Chem. Eur. J. 2018, 24, 16543. (h) Sharma, V.; Kaur, J.; Chimni, S. S. Eur. J. Org. Chem. 2018, 2018, 3489. (i) Li, F.; Pei, W.; Wang, J.; Liu, J.; Wang, J.; Zhang, M.-l.; Chen, Z.; Liu, L. Org. Chem. Front. 2018, 5, 1342. (j) Rout, S.; Joshi, H.; Singh, V. K. Org. Lett. 2018, 20, 2199. (3) For reviews, see: (a) Parra, A.; Tortosa, M. ChemCatChem 2015, 7, 1524. (b) Li, W.; Xu, X.; Zhang, P.; Li, P. Chem. - Asian J. 2018, 13, 2350. For selected examples, see: (c) Chu, W.-D.; Zhang, L.-F.; Bao, X.; Zhao, X.-H.; Zeng, C.; Du, J.-Y.; Zhang, G.-B.; Wang, F.-X.; Ma, X.-Y.; Fan, C.-A. Angew. Chem., Int. Ed. 2013, 52, 9229. (d) Caruana, L.; Kniep, F.; Johansen, T. K.; Poulsen, P. H.; Jørgensen, K. A. J. Am. Chem. Soc. 2014, 136, 15929. (e) Wang, Z.; Wong, Y. F.; Sun, J. Angew. Chem., Int. Ed. 2015, 54, 13711. (f) Dong, N.; Zhang, Z.-P.; Xue, X.-S.; Li, X.; Cheng, J.-P. Angew. Chem., Int. Ed. 2016, 55, 1460. (g) Zhao, K.; Zhi, Y.; Shu, T.; Valkonen, A.; Rissanen, K.; Enders, D. Angew. Chem., Int. Ed. 2016, 55, 12104. (h) Zhao, K.; Zhi, Y.; Wang, A.; Enders, D. ACS Catal. 2016, 6, 657. (i) Deng, Y.-H.; Zhang, X.-Z.; Yu, K.-Y.; Yan, X.; Du, J.-Y.; Huang, H.; Fan, C.-A. Chem. Commun. 2016, 52, 4183. (j) Zhang, X.-Z.; Deng, Y.-H.; Yan, X.; Yu, K.-Y.; Wang, F.-X.; Ma, X.-Y.; Fan, C.-A. J. Org. Chem. 2016, 81, 5655. (k) Wong, Y. F.; Wang, Z.; Sun, J. Org. Biomol. Chem. 2016, 14, 5751. (l) Li, X.; Xu, X.; Wei, W.; Lin, A.; Yao, H. Org. Lett. 2016, 18, 428. (m) Li, S.; Liu, Y.; Huang, B.; Zhou, T.; Tao, H.; Xiao, Y.; Liu, L.; Zhang, J. ACS Catal. 2017, 7, 2805. (n) Kang, T.-C.; Wu, L.-P.; Yu, Q.-W.; Wu, X.-Y. Chem. - Eur. J. 2017, 23, 6509. (o) Zhang, X.-Z.; Gan, K.-J.; Liu, X.-X.; Deng, Y.-H.; Wang, F.-X.; Yu, K.-Y.; Zhang, J.; Fan, C.-A. Org. Lett. 2017, 19, 3207. (p) Yan, J.; Chen, M.; Sung, H. H-Y.; Williams, I. D.; Sun, J. Chem. - Asian J. 2018, 13, 2440. (q) Santra, S.; Porey, A.; Jana, B.; Guin, J. Chem. Sci. 2018, 9, 6446. (r) Zhang, Z.-P.; Xie, K.-X.; Yang, C.; Li, M.; Li, X. J. Org. Chem. 2018, 83, 364. (s) Zhang, Z.-P.; Chen, L.; Li, X.; Cheng, J.-P. J. Org. Chem. 2018, 83, 2714. (t) Fan, Y.-J.; Zhou, L.; Li, S. Org. Chem. Front. 2018, 5, 1820. (u) Liu, Q.; Li, S.; Chen, X.-Y.; Rissanen, K.; Enders, D. Org. Lett. 2018, 20, 3622. (v) Wang, J.; Pan, X.; Liu, J.; Zhao, L.; Zhi, Y.; Zhao, K.; Hu, L. Org. Lett. 2018, 20, 5995. (w) Jiang, F.; Yuan, F.-R.; Jin, L.-W.; Mei, G.-J.; Shi, F. ACS Catal. 2018, 8, 10234. (x) Mei, G.; Xu, S.; Zheng, W.; Bian, C.; Shi, F. J. Org. Chem. 2018, 83, 1414. (y) Huang, G.-B.; Huang, W.-H.; Guo, J.; Xu, D.-L.; Qu, X.C.; Zhai, P.-H.; Zheng, X.-H.; Weng, J.; Lu, G. Adv. Synth. Catal. 2019, 361, 1241. (4) Fuson, R. C. Chem. Rev. 1935, 16, 1. (5) Chen, M.; Sun, J. Angew. Chem., Int. Ed. 2017, 56, 11966. (6) (a) Uraguchi, D.; Yoshioka, K.; Ueki, Y.; Ooi, T. J. Am. Chem. Soc. 2012, 134, 19370. (b) Yue, C.; Na, F.; Fang, X.; Cao, Y.; Antilla, J. C. Angew. Chem., Int. Ed. 2018, 57, 11004. (7) Qian, D.; Wu, L.; Lin, Z.; Sun, J. Nat. Commun. 2017, 8, 567.

diphenylthiazol-4(5H)-one 2f was isomerized to 2,5-diphenylthiazol-4-ol 2f′. Both aza-p-QM intermediate 1a′ and 2,5diphenylthiazol-4-ol 2f′ were synergistically activated by CPA5 via a bifunctional activation mode. Then, intramolecular conjugate addition generated 1,8-adduct 3af. In conclusion, we have developed an efficient and unified organocatalytic remote stereocontrolled 1,8-conjugate addition of aza-p-QMs generated in situ from propargylic alcohols. Importantly, asymmetric 1,8-conjugate addition of aza-p-QMs was well-established for the first time with the aid of chiral phosphoric acid. In particular, the construction of vicinal axially chiral tetrasubstituted allenes and sulfur-containing quaternary carbon stereocenters was achieved with high efficiency and stereoselectivity, which enriched the chemistry of chiral phosphoric acids. Control experiments provided important insights into the reaction mechanism. The transformation of the chiral 1,8-adduct was also investigated.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b02726. Experimental section, characterization details, and X-ray data (PDF) Accession Codes

CCDC 1941136 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■

REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected] or fl[email protected]. ORCID

Pengfei Li: 0000-0001-5836-1069 Wenjun Li: 0000-0001-9045-7845 Author Contributions §

L.Z. and Y.H. contributed equally to this work.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors are thankful for the financial support from the National Natural Science Foundation of China (21502043 and 21871128), the Special Funds of the Taishan Scholar Program D

DOI: 10.1021/acs.orglett.9b02726 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters (8) For selected reviews, see: (a) Sydnes, L. K. Chem. Rev. 2003, 103, 1133. (b) Brummond, K. M.; DeForrest, J. E. Synthesis 2007, 2007, 795. (c) Ogasawara, M. Tetrahedron: Asymmetry 2009, 20, 259. (d) Yu, S.; Ma, S. Chem. Commun. 2011, 47, 5384. (e) Ye, S.; Ma, S. Org. Chem. Front. 2014, 1, 1210. (f) Neff, R. K.; Frantz, D. E. ACS Catal. 2014, 4, 519. (9) (a) Hashimoto, T.; Sakata, K.; Tamakuni, F.; Dutton, M. J.; Maruoka, K. Nat. Chem. 2013, 5, 240. (b) Mbofana, C. T.; Miller, S. J. J. Am. Chem. Soc. 2014, 136, 3285. (c) Tap, A.; Blond, A.; Wakchaure, V. N.; List, B. Angew. Chem., Int. Ed. 2016, 55, 8962. (10) Zhang, P.; Huang, Q.; Cheng, Y.; Li, R.; Li, P.; Li, W. Org. Lett. 2019, 21, 503. (11) (a) Li, W.; Xu, X.; Liu, Y.; Gao, H.; Cheng, Y.; Li, P. Org. Lett. 2018, 20, 1142. (b) Li, W.; Yuan, H.; Liu, Z.; Zhang, Z.; Cheng, Y.; Li, P. Adv. Synth. Catal. 2018, 360, 2460. (c) Zhang, L.-L.; Liu, Y.; Liu, K.; Liu, Z.-T.; He, N.-N.; Li, W.-J. Org. Biomol. Chem. 2017, 15, 8743. (d) Zhang, L.-L.; Zhou, X.; Li, P.-F.; Liu, Z.-T.; Liu, Y.; Sun, Y.; Li, W.-J. RSC Adv. 2017, 7, 39216. (12) For reviews, see: (a) Itoh, T. Prog. Polym. Sci. 2001, 26, 1019. (b) Wojciechowski, K. Eur. J. Org. Chem. 2001, 2001, 3587. (c) Jaworski, A. A.; Scheidt, K. A. J. Org. Chem. 2016, 81, 10145. (d) Yang, B.; Gao, S. Chem. Soc. Rev. 2018, 47, 7926. (e) Schwan, J.; Christmann, M. Chem. Soc. Rev. 2018, 47, 7985. (13) (a) Lee, A.; Younai, A.; Price, C. K.; Izquierdo, J.; Mishra, R. K.; Scheidt, K. A. J. Am. Chem. Soc. 2014, 136, 10589. (b) Qi, S.; Liu, C.-Y.; Ding, J.-Y.; Han, F.-S. Chem. Commun. 2014, 50, 8605. (c) Liao, H.-H.; Chatupheeraphat, A.; Hsiao, C.-C.; Atodiresei, I.; Rueping, M. Angew. Chem., Int. Ed. 2015, 54, 15540. (d) Li, G.; Liu, H.; Lv, G.; Wang, Y.; Fu, Q.; Tang, Z. Org. Lett. 2015, 17, 4125. (e) Chatupheeraphat, A.; Liao, H.-H.; Mader, S.; Sako, M.; Sasai, H.; Atodiresei, I.; Rueping, M. Angew. Chem., Int. Ed. 2016, 55, 4803. (f) Kretzschmar, M.; Hodík, T.; Schneider, C. Angew. Chem., Int. Ed. 2016, 55, 9788. (g) Wang, L.; Li, S.; Blümel, M.; Philipps, A. R.; Wang, A.; Puttreddy, R.; Rissanen, K.; Enders, D. Angew. Chem., Int. Ed. 2016, 55, 11110. (h) Bera, K.; Schneider, C. Chem. - Eur. J. 2016, 22, 7074. (i) Bera, K.; Schneider, C. Org. Lett. 2016, 18, 5660. (j) Zhang, H.-H.; Wang, C.-S.; Li, C.; Mei, G.-J.; Li, Y.; Shi, F. Angew. Chem., Int. Ed. 2017, 56, 116. (k) Jia, H.; Liu, H.; Guo, Z.; Huang, J.; Guo, H. Org. Lett. 2017, 19, 5236. (l) Lee, A.; Zhu, J. L.; Feoktistova, T.; Brueckner, A. C.; Cheong, P. H.-Y.; Scheidt, K. A. Angew. Chem., Int. Ed. 2019, 58, 5941. (m) Liu, X.; Wang, K.; Guo, W.; Liu, Y.; Li, C. Chem. Commun. 2019, 55, 2668. (14) Chen, M.; Sun, J. Angew. Chem., Int. Ed. 2017, 56, 4583. (15) For our previous work on 5H-thiazol-4-ones, see: (a) Huang, Q.; Cheng, Y.; Yuan, H.; Chang, X.; Li, P.; Li, W. Org. Chem. Front. 2018, 5, 3226. (b) Zhang, L.; Yuan, H.; Lin, W.; Cheng, Y.; Li, P.; Li, W. Org. Lett. 2018, 20, 4970. (16) CCDC 1941136 (3jf). (17) For reviews on the construction of sulfur-containing quaternary carbon stereocenters, see: (a) Enders, D.; Lüttgen, K.; Narine, A. A. Synthesis 2007, 2007, 959. (b) Clayden, J.; MacLellan, P. Beilstein J. Org. Chem. 2011, 7, 582. (c) Liu, H.; Jiang, X. Chem. - Asian J. 2013, 8, 2546. (d) Zhao, X.; Shen, J.; Jiang, Z. Mini-Rev. Org. Chem. 2014, 11, 424. (e) Feng, M.; Tang, B.; Liang, S. H.; Jiang, X. Curr. Top. Med. Chem. 2016, 16, 1200. (f) Yu, J.-S.; Huang, H.-M.; Ding, P.-G.; Hu, X.-S.; Zhou, F.; Zhou, J. ACS Catal. 2016, 6, 5319.

E

DOI: 10.1021/acs.orglett.9b02726 Org. Lett. XXXX, XXX, XXX−XXX