Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/OrgLett
Palladium(0)−Lithium Iodide Cocatalyzed Asymmetric Hydroalkylation of Conjugated Enynes with Pronucleophiles Leading to 1,3-Disubstituted Allenes Hirokazu Tsukamoto,*,†,‡ Tatsuya Konno,† Kazuya Ito,† and Takayuki Doi† †
Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan Department of Pharmaceutical Sciences, Yokohama University of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama 245-0066, Japan
Downloaded via NEWCASTLE UNIV on August 23, 2019 at 23:09:59 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
‡
S Supporting Information *
ABSTRACT: Axially chiral 1,3-disubstituted allenes were synthesized via hydroalkylation of alkyl- or aryl-substituted conjugated enynes (readily prepared via a Sonogashira reaction) with pronucleophiles such as dimethyl malonate under the cocatalysis of DTBM-SEGPHOS-ligated palladium and lithium iodide. Although the palladium catalyst ligated with (S)-DTBMSEGPHOS prefers the formation of (R)-1,3-disubstituted allenes, lithium iodide recovers and increases the intrinsic selectivity producing (S)-allenes by promoting the isomerization of the exo-alkylidene-π-allylpalladium intermediate prior to the nucleophilic substitution step.
Scheme 1. Transformation of exo-Alkylidene-πallylpalladium 3 Generated from 3-Bromo-1,3-alkadiene 1, 2,3-Alkadienyl Acetate or Phosphate 2, and Conjugated Enyne 3 into Chiral 1,3-Disubstituted Allene 6
1,3-Disubstituted allenes with axial chirality are found in biologically active natural products and pharmaceuticals.1 Chiral allenes are also useful synthetic intermediates because a wide variety of reactions can be used to transfer the axial chirality to point chirality in the product.2 Optically active allenes can be conventionally synthesized using an SN2′ reaction of chiral propargyl alcohol derivatives, which are typically prepared via optical resolution of their acetate derivatives or the asymmetric reduction of their corresponding ketones.3 On the other hand, chiral allene 6 can be obtained from achiral or racemic substrates (1 and 2) bearing a leaving group through exo-alkylidene-πallylpalladium intermediate 3 ligated with a chiral phosphine ligand (Scheme 1).4−6 However, the preparation of 1 and 2 requires multiple steps from commercially available materials and their transformation into allene 6 requires a stoichiometric amount of base, leading to the formation of salts as byproducts. To solve these problems, we planned to generate intermediate 3 from conjugated enyne 7 via hydropalladation,7 i.e., the concomitant protonation and oxidative addition to palladium(0) (vide infra). Enyne 7 can be readily prepared using a Sonogashira reaction between a terminal alkyne and vinyl bromide, and undergo the addition of pronucleophiles 5 under neutral conditions. Yamamoto’s group reported the synthesis of achiral 1-substituted or 1,1-disubstituted allenes via a related coupling reaction between 1-alkenyl-substituted terminal alkynes and cyano-containing pronucleophiles in the presence of Pd2dba3·CHCl3 and 1,1′-bis(diphenylphosphino)ferrocene (dppf) in THF.8 They also proposed a reaction mechanism consisting of (1) oxidative addition of the pronucleophile to palladium(0), (2) regioselective hydropalladation (or carbo© XXXX American Chemical Society
palladation) of the alkyne, and (3) reductive coupling, although any proof such as stereochemical information to support this mechanism was not given. Herein, we report effective reaction conditions for the palladium(0)-catalyzed asymmetric hydroalkylation of internal conjugated enynes 7 with pronucleophiles, such as substituted and unsubstituted malonates.9−11 We also prove that the 1,4-addition of a proton and the carbonucleophile occurs with syn-selectivity via a predominant anti-hydropalladation step and subsequent nucleophilic substitution with inversion of stereochemistry. Received: July 14, 2019
A
DOI: 10.1021/acs.orglett.9b02439 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters
contrast to Ogasawara and Hayashi’s work, the use of dibenzylideneacetone-ligated palladium complexes did not increase the enantioselectivity (entries 2 and 3). The addition of a catalytic amount of salt was examined because the low and opposite enantioselectivity observed in our reaction may be derived from its salt-free conditions. Neither lithium acetate, which was employed by Nemoto and Hamada for the asymmetric substitution reaction of 2,3-alkadienyl phosphate, nor its potassium salt improved the enantioselectivity (entries 4 and 5). However, the addition of lithium halides reversed the enantioselectivity to give product 6aA with the (S)-enantiomer obtained as the major component (entry 1 vs entries 6−8). At this point, the enantioselectivity of the hydroalkylation of 7a with 5A was identical to that of the palladium-catalyzed substitution reaction using 1a and 2a.5,6 The enantioselectivity of the reaction with lithium iodide was further improved by decreasing the reaction temperature to 50 °C (entry 8 vs 9). The catalyst loading can be decreased to 5 mol % without any significant reduction in the yield and enantioselectivity (entry 10). The additive can also be reduced to the same amount as the palladium catalyst with little effect on the enantioselectivity (entries 10−13). The reaction proceeded even at room temperature (entry 12). Using the optimized conditions shown in Table 1, entry 13, the scope of the conjugated enyne substrate and pronucleophile was explored (Figure 1). Enynes 7b−d (R = Cy, Ph, and tBu)
Initially, the reaction conditions for the hydroalkylation of internal alkyne 7a with dimethyl malonate (5A) were screened (Table 1). The reactions were performed using 5A (3.0 Table 1. Optimization of the Asymmetric Hydroalkylation of 7a with 5A
Entry 1 2 3 4 5 6 7 8 9 10 11 12 13
Pd catalyst (allyl)CpPd (10 mol %) Pd2dba3·CHCl3 (5 mol %) Pd(dba)2 (10 mol %) (allyl)CpPd (10 mol %) (allyl)CpPd (10 mol %) (allyl)CpPd (10 mol %) (allyl)CpPd (10 mol %) (allyl)CpPd (10 mol %) (allyl)CpPd (10 mol %) (allyl)CpPd (5 mol %) (allyl)CpPd (5 mol %) (allyl)CpPd (5 mol %) (allyl)CpPd (5 mol %)
Additive
Temp (°C)
Yield (%)a
Er (S/R) (%)b
none
65
nd (81)
29:71
none
65
nd (83)
33:67
none
65
28:72
LiOAc (30 mol %) KOAc (30 mol %) LiCl (30 mol %) LiBr (30 mol %) LiI (30 mol %) LiI (30 mol %) LiI (30 mol %) LiI (15 mol %) LiI (15 mol %) LiI (5 mol %)
65
nd (quant) 94 (78)
65
100 (78)
25:75
65
95 (77)
68:32
65
93 (81)
76:24
65
nd (90)
78:22
50
95
83:17
50
99
86:14
50
quant
84:16
rt
quant
86:14
50
98 (84)
85:15
28:72
a
The yield was determined using 1H NMR spectroscopy with 1,1,2,2tetrachloroethane as an internal standard. The isolated yields are shown in the parentheses. bThe enantiomeric ratio was determined using chiral HPLC.
Figure 1. Scope of conjugated enynes 7b−d and pronucleophiles 5A− G investigated in the hydroalkylation reaction.
equiv),12 allyl(cyclopentadienyl)palladium(II) (10 mol %), and a variety of diphosphine ligands (15 mol %) at 65 °C in methanol, which we expected to function as a proton source. Among achiral and chiral bis(diarylphosphine) ligands we tested (see Supporting Information), axially chiral SEGPHOS bearing electron-rich bis(3,5-di-tert-butyl-4-methoxyphenyl, DTBM) groups on the phosphorus atoms gave 6aA in good yield (entry 1). Interestingly, the major enantiomer of product 6aA obtained using the (S)-DTBM-SEGPHOS did not match that prepared via the substitution reaction of 3-bromo-1,3-dienes 1a (R = octyl) and 2,3-alkadienyl phosphate 2a (R = octyl, X = OPO(OEt)2) with 5A using the (S)-biaryl-based ligand in the presence of Pd 2 dba 3 . 5,6 To improve (or reverse) the enantioselectivity using the DTBM-SEGPHOS ligand, the reaction conditions were further optimized by testing different palladium sources and additives that can promote the isomerization between the two exo-alkylidene-π-allylpalladium species (3 and 3′) via coordination and stabilization of alkenyl intermediate 4 (Scheme 1) (Table 1, entries 2−13).13 In
substituted with secondary and tertiary alkyl, and aryl groups at the alkyne terminus, also underwent the asymmetric hydroalkylation with 5A to afford allenes 6(b−d)A in excellent yield. The enantioselectivities of the products were much higher than those observed for octyl-substituted enyne 7a. A substituent at C-2 in dimethyl malonate was tolerated to give corresponding allenes 6d(B−D) in moderate to good yield with high enantioselectivity. Bis(phenylsulfonyl)methane (5E) also participated in the enantioselective conversion of 7b and 7d into 1,3-disubstituted allenes 6bE and 6dE, respectively. Both the reaction yield and optical purity of allenes 6bF and 6bG prepared via the hydroalkylation of 7b with acetylacetone (5F) and malononitrile (5G) were lower than those observed for 6bA and 6bE. To obtain insight into the stereochemistry of the hydroalkylation reaction of enyne 7 with pronucleophile 5A, deuterium-labeled enyne 7b-d with an E-configuration was prepared and subjected to the reaction using achiral diphosphine ligand 8 in the absence of lithium iodide (Scheme 2). The resulting product 6bA-d was obtained as a 3:1 diastereomeric B
DOI: 10.1021/acs.orglett.9b02439 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters
hydroalkylation of enyne 7a in the absence of lithium iodide shows that, in the initial hydropalladation step, the chiral diphosphine ligand prefers the formation of the opposite exoalkylidene-π-allylpalladium species, which leads to the minor enantiomer and that the nucleophilic substitution step precedes the isomerization process.
Scheme 2. syn-Selective Hydroalkylation of 7b-d with 5A
Scheme 3. Overall Retention of Stereochemistry Observed in the Substitution Reaction of 2b-d with 5A and the Effect of Lithium Iodide on the Chirality Transfer Pathway
mixture, which was determined using 1H NMR analysis of γlactones 10-d and 11-d prepared from 6bA-d via saponification of the methyl ester groups, decarboxylation, and stereoselective iodolactonization using the procedure of Ma.14 The stereochemistries of 10-d and 11-d were established by their NOESY spectra. While the methine proton at γ-position in 10-d had NOE with the vinyl proton and no NOE with the major residual proton as X at the β-position, the γ-proton in 11-d had NOE with the major residual proton as X and no NOE with the vinyl proton. The chemical shifts of geminal protons at β-positions in 10-d and 11-d also agreed with those reported for γ-vinyl-γbutyrolactone, where the vinyl group shielded and deshielded the cis- and trans-protons, respectively.15 These assignments established the stereochemistry of 6bA-d, as shown in Scheme 2. The diastereoselectivity observed in the hydroalkylation reaction indicates that the 1,4-addition of the proton and nucleophile (deprotonated 5A) to 7b-d occurred with synselectivity. The exo-alkylidene-π-allylpalladium intermediate generated via hydropalladation of conjugated enyne 7b-d in the presence of pronucleophile 5A can also be formed in the substitution reaction of 2,3-alkadienyl carbonate 2b-d with 5A via oxidative addition of 2b-d to the palladium(0) complex, decarboxylation, and deprotonation of pronucleophile 5A. An overall retention of the configuration was observed in the substitution reaction of 2b-d with 5A with achiral ligand 8 in the absence of lithium iodide (Scheme 3), which indicated that the oxidative addition and nucleophilic substitution steps should occur via a double inversion of stereochemistry, as observed in the Tsuji−Trost reaction.16 This result strongly supports that the syn-selective hydroalkylation was initiated by a preferential anti-hydropalladation step, i.e., anti-protonation of the conjugated enyne coordinated by electron-rich palladium(0).17 The syn-selectivity observed in the hydroalkylation reaction of conjugated enyne 7b-d is also potentially consistent with the reaction mechanism proposed by Yamamoto, i.e., the oxidative addition of the pronucleophile to palladium(0) followed by syn-hydropalladation and reductive elimination. However, soft carbonucleophiles rarely undergo reductive elimination with retention of stereochemistry.16 In addition, chirality transfer of (Sa,R)-2b-d into 6bA-d was insufficient and was completely lost upon the addition of lithium iodide (Scheme 3). A lack of chirality transfer is required for the dynamic kinetic asymmetric substitution reaction of 2,3alkadienyl phosphate 2 and the asymmetric hydroalkylation of 7. This result was consistent with the hypothesis that the additive can improve the enantioselectivity of the reaction by promoting the isomerization between exo-alkylidene-π-allylpalladium species 3 and 3′ via stabilization of alkenyl intermediate 4 (Scheme 1). The reverse enantioselectivity observed in the
In summary, we have developed a palladium(0)−lithium iodide cocatalyzed hydroalkylation reaction to synthesize axially chiral 1,3-disubstituted allenes from conjugated enynes, which are readily prepared via a Sonogashira reaction between a terminal alkyne and vinyl bromide. The reaction does not need the addition of a stoichiometric amount of additive or produce any byproducts. The reaction proceeds via a syn-selective 1,4addition of a proton and nucleophile to the conjugated enyne, which is derived from an anti-hydropalladation step followed by nucleophilic substitution with inversion of stereochemistry. A mechanistic study on the anti-selective hydropalladation step is currently underway in our laboratory.
■
ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b02439. Detailed experimental procedures, spectroscopic data, and copies of NMR spectra (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Hirokazu Tsukamoto: 0000-0002-7849-6427 Takayuki Doi: 0000-0002-8306-6819 Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was partly supported by The Research Foundation for Pharmaceutical Sciences, SUNTRY FOUNDATION for LIFE SCIENCES, Platform Project for Supporting Drug Discovery C
DOI: 10.1021/acs.orglett.9b02439 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters
M.; Kadota, I.; Saito, S.; Yamamoto, Y. Tetrahedron 1997, 53, 9097− 9106. (9) A related series of asymmetric hydrometalation of conjugated enynes have been reported. Hydroboration: (a) Matsumoto, Y.; Naito, M.; Uozumi, Y.; Hayashi, T. J. Chem. Soc., Chem. Commun. 1993, 1468− 1469. (b) Gao, D.-W.; Xiao, Y.; Liu, M.; Liu, Z.; Karunananda, M. K.; Chen, J. S.; Engle, K. M. ACS Catal. 2018, 8, 3650−3654. (c) Sang, H. L.; Yu, S.; Ge, S. Org. Chem. Front. 2018, 5, 1284−1287. (d) Huang, Y.; del Pozo, J.; Torker, S.; Hoveyda, A. H. J. Am. Chem. Soc. 2018, 140, 2643−2655. Hydrosilylation: (e) Han, J. W.; Tokunaga, N.; Hayashi, T. J. Am. Chem. Soc. 2001, 123, 12915−12916. (f) Ogasawara, M.; Ito, A.; Yoshida, K.; Hayashi, T. Organometallics 2006, 25, 2715−2718. (g) Wang, M.; Liu, Z.-L.; Zhang, X.; Tian, P.-P.; Xu, Y.-H.; Loh, T.-P. J. Am. Chem. Soc. 2015, 137, 14830−14833. (10) Asymmetric hydroarylation and -alkylation of conjugate enynes substituted by an electron-withdrawing group have been reported. (a) Hayashi, T.; Tokunaga, N.; Inoue, K. Org. Lett. 2004, 6, 305−307. (b) Nishimura, T.; Makino, H.; Nagaosa, M.; Hayashi, T. J. Am. Chem. Soc. 2010, 132, 12865−12867. (c) Qian, H.; Yu, X.; Zhang, J.; Sun, J. J. Am. Chem. Soc. 2013, 135, 18020−18023. (d) Yao, Q.; Liao, Y.; Lin, X.; Ji, J.; Liu, X.; Feng, X. Angew. Chem., Int. Ed. 2016, 55, 1859−1863. (11) Recently, asymmetric hydroamination of neutral conjugated enynes was reported. Adamson, N. J.; Jeddi, H.; Malcolmson, S. J. J. Am. Chem. Soc. 2019, 141, 8574−8583. (12) It should be noted that the use of an excess amount of dimethyl malonate (5A) (3.0 equiv) was necessary to prevent the resulting allene 6aA from undergoing a 1,4-addition reaction with 7a leading to the dialkylated product. In addition, under the reaction conditions, 1,3disubstituted allene 6aA was not susceptible to further hydroalkylation with 5A to give the corresponding allylic compound.18 (13) Exo-alkylidene-π-allylpalladium: (a) Benyunes, S. A.; Brandt, L.; Fries, A.; Green, M.; Mahon, M. F.; Papworth, T. M. T. J. Chem. Soc., Dalton Trans. 1993, 3785−3793. (b) Ogasawara, M.; Okada, A.; Watanabe, S.; Fan, L.; Uetake, K.; Nakajima, K.; Takahashi, T. Organometallics 2007, 26, 5025−2029 and see also ref 6a . (14) Stereoselective iodolactonization of allenic acid: (a) Jiang, X.; Fu, C.; Ma, S. Chem. Eur. J. 2008, 14, 13501−13509. (b) Zhang, X.; Fu, C.; Yu, Y.; Ma, S. Chem. - Eur. J. 2012, 18, 13501−13509. (15) (a) Pihlaja, K.; Riddell, F. G.; Jalonen, J.; Rinta-Panttila, P.; Anteunis, M. Org. Magn. Reson. 1974, 6, 301−302. (b) Abraham, R. J.; Leonard, P. Magn. Reson. Chem. 2013, 51, 9−15. (16) (a) Jolly, P. W. Angew. Chem., Int. Ed. Engl. 1985, 24, 283−295. (b) Tsuji, J. In Handbook of Organopalladium Chemistry for Organic Synthesis, Vol. 2; Negishi, E., Ed.; WILEY: New York, 2002; pp 1669− 1687. (c) Acemoglu, L.; Williams, J. M. J. In Handbook of Organopalladium Chemistry for Organic Synthesis, Vol. 2; Negishi, E., Ed.; WILEY: New York, 2002; pp 1689−1705. (d) Poli, G.; Prestat, G.; Liron, F.; Kammerer-Pentier, C. Top. Organomet. Chem. 2011, 38, 1− 64. (17) Anti-hydropalladation was proposed for the anti-selective hydroalkoxylation of conjugated diynes: Camacho, D. H.; Saito, S.; Yamamoto, Y. Tetrahedron Lett. 2002, 43, 1085−1088. (18) (a) Yamamoto, Y.; Al-Masum, M.; Asao, N. J. Am. Chem. Soc. 1994, 116, 6019−6020. (b) Yamamoto, Y.; Al-Masum, M.; Fujiwara, N.; Asao, N. Tetrahedron Lett. 1995, 36, 2811−2814. (c) Yamamoto, Y.; Al-Masum, M. Synlett 1995, 1995, 969−970. (d) Yamamoto, Y.; AlMasum, M.; Fujiwara, N. Chem. Commun. 1996, 381−382. (e) Yamamoto, Y.; Al-Masum, M.; Takeda, A. Chem. Commun. 1996, 831−832. (f) Patil, N. T.; Pahadi, N. K.; Yamamoto, Y. Synthesis 2004, 2004, 2186−2190. (g) Trost, B. M.; Gerusz, V. J. J. Am. Chem. Soc. 1995, 117, 5156−5157. (h) Trost, B. M.; Michellys, P.-Y.; Gerusz, V. J. Angew. Chem., Int. Ed. Engl. 1997, 36, 1750−1753.
and Life Science Research (Basis for Supporting Innovative Drug Discovery and Life Science Research (BINDS)) from AMED under Grant Number JP18am0101095 and JP18am0101100, and JSPS KAKENHI Grant Numbers JP19K06966 and JP15H05837 in Middle Molecular Strategy.
■
REFERENCES
(1) Reviews: (a) Hoffmann-Röder, A.; Krause, N. Angew. Chem., Int. Ed. 2004, 43, 1196−1216. (b) Krause, N.; Hoffmann-Röder, A. In Modern Allene Chemistry, Vol. 2; Krause, N., Hashmi, A. S. K., Eds.; Wiley-VCH: Weinheim, 2004; pp 997−1032. (c) Brummond, K. M.; Chen, H. In Modern Allene Chemistry, Vol. 2; Krause, N., Hashmi, A. S. K., Eds.; Wiley-VCH: Weinheim, 2004; pp 1041−1089. (d) Yu, S.; Ma, S. Angew. Chem., Int. Ed. 2012, 51, 3074−3112. (2) Reviews: (a) Ma, S. Acc. Chem. Res. 2003, 36, 701−712. (b) Ma, S. Acc. Chem. Res. 2009, 42, 1679−1688. (c) Ye, J.; Ma, S. Acc. Chem. Res. 2014, 47, 989−1000. (d) Krause, N.; Winter, C. Chem. Rev. 2011, 111, 25−36. (e) Krause, N.; Belting, V.; Deutsch, C.; Erdsack, J.; Fan, H.-T.; Gockel, B.; Hoffmann-Röder, A.; Morita, N.; Volz, F. Pure Appl. Chem. 2008, 80, 1063−1069. (f) Krause, N.; Aksin-Artok, Ö .; Breker, V.; Deutsch, C.; Gockel, B.; Poonoth, M.; Sawama, Y.; Sawama, Y.; Sun, T.; Winter, C. Pure Appl. Chem. 2010, 82, 1529−1536. (g) Krause, N.; Aksin-Artok, Ö .; Asikainen, M.; Breker, V.; Deutsch, C.; Erdsack, J.; Fan, H.-T.; Gockel, B.; Minkler, S.; Poonoth, M.; Sawama, Y.; Sawama, Y.; Sun, T.; Volz, F.; Winter, C. J. Organomet. Chem. 2012, 704, 1−8. (h) Yang, M.; Hashmi, A. S. K. Chem. Soc. Rev. 2014, 43, 2941−2955. (i) Neff, R. K.; Frantz, D. E. Tetrahedron 2015, 71, 7−18. (j) Alonso, J. M.; Quirós, M. T.; Muñoz, M. P. Org. Chem. Front. 2016, 3, 1186− 1204. (3) Reviews: Alexakis, A. Pure Appl. Chem. 1992, 64, 387−392. (4) Recent reviews on synthesis of allenes: (a) Krause, N.; HoffmannRöder, A. Tetrahedron 2004, 60, 11671−11694. (b) Hashmi, A. S. K. In Modern Allene Chemistry, Vol. 1; Krause, N., Hashmi, A. S. K., Eds.; Wiley-VCH: Weinheim, 2004; pp 3−50. (c) Hoffmann-Röder, A.; Krause, N. In Modern Allene Chemistry, Vol. 1; Krause, N., Hashmi, A. S. K., Eds.; Wiley-VCH: Weinheim, 2004; pp 51−92. (d) Ogasawara, M.; Hayashi, T. In Modern Allene Chemistry, Vol. 1; Krause, N., Hashmi, A. S. K., Eds.; Wiley-VCH: Weinheim, 2004; pp 93−140. (e) Ohno, H.; Nagaoka, Y.; Tomioka, K. In Modern Allene Chemistry, Vol. 1; Krause, N., Hashmi, A. S. K., Eds.; Wiley-VCH: Weinheim, 2004; pp 141−181. (f) Ogasawara, M. Tetrahedron: Asymmetry 2009, 20, 259−271. (g) Yu, S.; Ma, S. Chem. Commun. 2011, 47, 5384−5418. (h) Ye, J.; Ma, S. Org. Chem. Front. 2014, 1, 1210−1224. (i) Chu, W.-D.; Zhang, Y.; Wang, J. Catal. Sci. Technol. 2017, 7, 4570−4579. (5) From 3-halo- or pseudohalo-1,3-diene: (a) Ogasawara, M.; Ikeda, H.; Nagano, T.; Hayashi, T. J. Am. Chem. Soc. 2001, 123, 2089−2090. (b) Ogasawara, M.; Ueyama, K.; Nagano, T.; Mizuhata, Y.; Hayashi, T. Org. Lett. 2003, 5, 217−219. (c) Ogasawara, M.; Nagano, T.; Hayashi, T. J. Org. Chem. 2005, 70, 5764−5767. (d) Ogasawara, M.; Ngo, H. L.; Sakamoto, T.; Takahashi, T.; Lin, W. Org. Lett. 2005, 7, 2881−2884. (e) Ogasawara, M.; Ge, Y.; Uetake, K.; Takahashi, T. Org. Lett. 2005, 7, 5697−5700. (6) From 2,3-alkadienyl phosphate or acetate: (a) Imada, Y.; Ueno, K.; Kutsuwa, K.; Murahashi, S.-I. Chem. Lett. 2002, 31, 140−141. (b) Trost, B. M.; Fandrick, D. R.; Dinh, D. C. J. Am. Chem. Soc. 2005, 127, 14186−14187. (c) Imada, Y.; Nishida, M.; Kutsuwa, K.; Murahashi, S.-I.; Naota, T. Org. Lett. 2005, 7, 5837−5839. (d) Imada, Y.; Nishida, M.; Naota, T. Tetrahedron Lett. 2008, 49, 4915−4917. (e) Nemoto, T.; Kanematsu, M.; Tamura, S.; Hamada, Y. Adv. Synth. Catal. 2009, 351, 1773−1778. (f) Boutier, A.; KammererPentier, C.; Krause, N.; Prestat, G.; Poli, G. Chem. - Eur. J. 2012, 18, 3840−3844. (7) Review: (a) Yamamoto, Y.; Radhakrishnan, U. Chem. Soc. Rev. 1999, 28, 199−207. (b) Trost, B. M. Chem. - Eur. J. 1998, 4, 2405. (c) Grushin, V. V. Chem. Rev. 1996, 96, 2011−2033. (8) (a) Salter, M. M.; Gevorgyan, V.; Saito, S.; Yamamoto, Y. Chem. Commun. 1996, 17−18. (b) Gevorgyan, V.; Kadowaki, C.; Salter, M. D
DOI: 10.1021/acs.orglett.9b02439 Org. Lett. XXXX, XXX, XXX−XXX
