A General Nickel-Catalyzed Kumada Vinylation for the Preparation of

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A General Nickel-Catalyzed Kumada Vinylation for the Preparation of 2-Substituted 1,3-Dienes Daniele Fiorito, Sarah Folliet, Yangbin Liu, and Clément Mazet ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.7b04030 • Publication Date (Web): 05 Jan 2018 Downloaded from http://pubs.acs.org on January 5, 2018

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A General Nickel-Catalyzed Kumada Vinylation for the Preparation of 2-Substituted 1,3-Dienes Daniele Fiorito, Sarah Folliet, Yangbin Liu, Clément Mazet* Department of Organic Chemistry, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva, Switzerland. ABSTRACT: The identification of two nickel(II) precatalysts for the preparation of 2-substituted 1,3-dienes by a Kumada cross-coupling between vinyl magnesium bromide and vinyl phosphates is described. This is noteworthy as engaging already only one vinyl derivative in a transition metal-catalyzed cross-coupling reaction is reputedly challenging. Salient features of this method are its operational simplicity, the mild reaction conditions, the low catalyst loadings, the short reaction times, its scalability, and the use of stoichiometric quantities of each coupling partner. The tolerance of the two nickel catalysts to an important number of reactive functional groups and their compatibility with structurally complex molecular architectures has been extensively delineated. A Negishi variant of the reaction has been developed for even more sensitive organic functions such as ester or nitrile. Several other conjugated 1,3-dienes with various substitution patterns have been prepared by combining commercial alkenyl Grignard reagents and/or readily available alkenyl enol phosphates. Proper choice of the nickel catalyst and of the reaction temperature gave access to a variety of different olefin isomers with high levels of stereocontrol. In fine, this approach affords conjugated dienes that would not be accessible otherwise and therefore provides a valuable complement to existing methods.

KEYWORDS: nickel catalysis, cross-coupling, Grignard reagents, conjugated 1,3-dienes, selective catalysis ■ INTRODUCTION Owing to their importance as building blocks in the synthesis of fine chemicals, natural products and functional polymers, the development of a general method for the preparation of 2-substituted 1,3-dienes represents a contemporary challenge in chemistry (Figure 1, A-B).1 To date, Ru-catalyzed cross-metathesis between terminal alkynes and ethylene (i.e. ene-yne metathesis) is the most straightforward route for the preparation of acyclic 2substituted dienes. Nonetheless, the scope of this method is limited by the combination of two synthons with inherently restricted structural diversity (Figure 1, C).2 Among other alternatives, the Ni- or Pd-catalyzed Kumada and Negishi-type cross-coupling reactions using Grignard reagents derived from chloroprene are in principle attractive because of the potential diversity of the electrophilic coupling partners (Figure 1, D).3 Yet, the instability of these organomagnesium species and the limited functional group tolerance associated with such highly reactive reagents imparts severe limitations. Interestingly, this strategy has been extensively employed by the Sherburn group to access and study dendralenes and natural products derived thereof.4 Using the same disconnection but reversing the polarity between both fragments, Claesson and later Bäckvall reported Ni-catalyzed cross-couplings between dienyl phosphates and a handful of Grignard reagents enabling the preparation of a small set of acyclic

and cyclic 1,3-dienes (Figure 1, E).5 We recently disclosed two complementary catalytic systems (a Brønsted acid and a cationic iridium complex) for the vinylogous Peterson elimination of silylated allylic alcohols leading to the formation of a broad variety of 2-subtituted 1,3-dienes (Figure 1, F).6 Both systems are compatible with a wide number of sensitive functional groups and afford a variety of structurally complex 2-substituted 1,3-dienes as well as to more substituted conjugated dienes. Unfortunately, the usefulness of the method is thwarted by the long and linear synthetic sequence upstream from substrate synthesis. At the outset of our investigations, we envisaged that 2-substituted 1,3-dienes could be accessed by crosscoupling between a vinyl metal donor and a vinyl halide or pseudo-halide. Although simple at first glance, this disconnection imposes to rise to the challenges associated with cross-coupling of vinyl nucleophiles and vinyl electrophiles – two coupling partners which are notoriously more difficult to tame than their aryl or alkenyl counterparts.7 Here, we disclose the successful realization of our objective with the identification of two practical and general Ni-catalysts operating under very mild reaction conditions for the preparation of 2-substituted 1,3-dienes starting from readily available enol phosphates and commercial vinyl magnesium bromide (Figure 1, G).8 This process is compatible with a variety of functional groups,

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Figure 1. (A) General structure of 2-substituted 1,3-dienes. (B) Naturally occurring 2-substituted 1,3-dienes. (C) Rucatalyzed enyne cross-metathesis. (D) Pd- and Ni-catalyzed cross-coupling using dienyl organomagnesium reagents. (E) Ni-catalyzed cross-coupling using dienyl phosphates. (F) Ir- or Brønsted acid-catalyzed vinylogous Peterson elimination. (G) Current work: Ni-catalyzed cross-coupling between vinyl phosphates and vinyl magnesium reagents. accommodates structurally complex scaffolds and also enables preparation of more substituted conjugated 1,3dienes with high levels of stereocontrol using alkenyl Grignard reagents and/or substituted enol phosphates.

Table 1. Reaction optimizationa

■ RESULTS AND DISCUSSION Reaction optimization. Our study commenced by evaluating several nickel precatalysts 1a-h for the crosscoupling reaction between diethyl-(1-phenylvinyl)phosphate 2a and vinyl magnesium bromide 3a (Table 1).9 No reaction occurred in the absence of nickel catalyst (Entry 1). Consumption of enol phosphate 2a was observed with 1a-c but only traces of 4aa could be detected (Entry 2-4). Gratifyingly, the use of the commercial precatalyst [(dppe)NiCl2] 1d showed 85% conversion into 4aa (Entry 5). Variation of the bite angle of the chelating ligand led to contrasted results as [(dppm)NiCl2] 1d gave only modest conversion into 4aa (Entry 6) and [(dppp)NiCl2] 1e was found to be essentially as productive as 1d (Entry 7). While increasing the relative stoichiometry in vinyl magnesium bromide proved detrimental (Entry 8), the use of an almost equimolar amount of 3a with respect to 2a gave the best result and 4aa was isolated in 92% yield (Entry 9). Two additional catalysts with an ethane bridge chelating bisphosphine ligand 1g-h were also evaluated and displayed similar reactivity to 1d (Entry 10-11). Reaction scope. The commercial availability and the robustness of 1d prompted us to investigate the scope of the transformation using this precatalyst for an array of enol phosphates - themselves prepared in one step and in high yield from the corresponding commercially available methyl ketones (See Supporting Information). Most of the

entry

catalyst

3a (x equiv.)

4aa conv. (%)

1

none

1.20

99 (85) b

1

Reaction conditions: 2a (0.5 mmol). Determined by H NMR of the crude reaction mixture. In parenthesis, yield of isolated product after purification by column chromatogc d raphy. dppe: 1,2-bis-(diphenylphosphino)ethane. dppm: e 1,2-bis-(diphenylphosphino)methane. dppp: 1,2-bisf (diphenylphosphino)propane. dmpe: 1,2-bisg (dimethylphosphino)ethane. depe: 1,2-bis(diethylphosphino)ethane.

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Figure 2. Substrate scope (0.5-10 mmol; vinyl magnesium bromide: 1.05 equivalents). Isolated yields after column chromatography. In red: yields obtained using catalyst 1d. In blue: yields obtained using catalyst 1g. (a) 5 mol%; (b) 15 minutes; (c) 5 mol%, 2.10 equiv. of 3a; (d) 10 mol%, 24 h, 0.1 M; (e) Isolated as Diels-Alder adduct using N-methyl maleimide as dienophile (See Supporting Information). Yield after two steps; (f) Along with 22% of proto-demetallated substrate; (g) 5 mol%, 4 h, 0.1 M. products displayed on Figure 2 were obtained in high yield with a loading as low as 2.5 mol% and within 1 h at room temperature. Electron-rich, electron-neutral and electron-deficient aryl derivatives possessing substituents at various position of the aromatic ring were all competent substrates and the resulting 2-substituted 1,3dieneswere isolated in yields ranging from 61 to 90% (4aa-4na, 14 examples, average yield = 81%). Of particular interest, in this series, several functionalized substrates (4ca, 4ea, 4fa, 4ga, 4ja, 4na) can be potentially engaged as electrophiles in an orthogonal cross-coupling reaction under nickel catalysis - thus further underscoring the mildness of the present method.10 Nonetheless, catalyst 1d did not prove adequate with several other vinyl phosphates leading to either traces or very low yield of the targeted 1,3-dienes (4oa-4ua). This prompted us to resort to [(dmpe)NiCl2] (1g) the second best candidate identified

upon optimization of the reaction conditions (vide supra). Much of our satisfaction, products with a trifluoromethyl, a fluorine, a chlorine and a protected alkyne in para position were isolated in practical yield. Similarly, a bis-vinyl phosphate and indenyl scaffolds were cross-coupled successfully using 1g (4sa, 4ta, 4ua). The same approach was followed for heteroaromatic and alkyl precursors. In most cases, [(dppe)NiCl2] proved to be the catalyst of choice. For more difficult substrates, 1g was used as a satisfactory alternative (4ya, 4b’a, 4j’a, 4k’a). More importantly, the nature of the functional groups and the structural diversity tolerated by either catalyst is particularly noticeable. For instance, many of the alkyl substrates surveyed do possess reactive alkene moieties or epimerizable stereocenters in their skeleton, all of which turned out to be unaffected under the reaction conditions.

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Figure 3. Negishi variant of the nickel-catalyzed crosscoupling of vinyl phosphates with vinyl magnesium bromide (0.25-1.5 mmol). Vinyl magnesium bromide: 1.2 equivalents. Isolated yields after column chromatography.

Figure 4. (A) Evaluation of the lower limits in catalyst loading with 1d and 1g. (B) Scale up experiments. A complementary protocol was developed for vinyl phosphates bearing particularly sensitive carbonyl functionalities such as an O-acyl (2l’a), an ester (2m’a) or a nitrile (2n’a) (Figure 3).11 Preparation of the milder nucleophilic vinylzinc reagent was performed in situ from vinyl magnesium bromide prior to addition of the nickel precatalyst (2.5-5.0 mol%) and the appropriate enol phosphate under otherwise identical conditions. Using this approach, 4l’a, 4m’a and 4n’a were obtained in 64-70% yield. When the loading in nickel precatalyst was decreased to 1.0 mol% with [(dppe)NiCl2] in the model crosscoupling reaction between 2a and 3a, diene 4aa was obtained in a slightly reduced yield (60% vs. 85%). Remarkably, [(dmpe)NiCl2] maintained an excellent level of catalytic efficiency even at a loading as low as 0.1 mol%, affording 4aa in 85% yield (Figure 4-A). The practicality of our method was further demonstrated by conducting multi- gram scale experiments in the coupling between 2c and 3a (Figure 4-B). For instance, 1.1 g of 4ca can be readily prepared within 1 h at room temperature using only 6 mg of nickel complex 1g and a stoichiometric amount of each coupling partner. Alkenyl Grignard reagents. Although our initial objective was directed towards the development of a general protocol for the synthesis of 2-substituted 1,3-dienes, we next explored the possibility to extend our method to the preparation of 1,3-dienes with higher substitution patterns starting from alkenyl phosphates and/or alkenyl Grignard reagents.

A series of commercially available alkenyl Grignard reagents 3b-e was investigated using 2c and 2o as representative substrates for the aryl and alkyl series of vinyl phosphates respectively (Figure 5). Using the optimized conditions and [(dppe)NiCl2] as precatalyst, isoprenyl magnesium bromide 3b and 2-methylpropenyl magnesium bromide 3c could be cross-coupled efficiently with both vinyl phosphates affording 4cb, 4ob, 4cc and 4oc in 74%, 73%, 77% and 79% yield respectively. Using a commercial source of propenyl magnesium bromide 3d (E/Z = 45:55), 4cd and 4o’d were isolated in 85% and 76% yield respectively as ~1:1 stereoisomeric mixtures. Similar results were obtained with 1g, 4cd and 4o’d were isolated in 68% and 74% yield (E/Z = 50:50). When employing 1methylpropenyl magnesium bromide 3e (E/Z = 75:25), the coupling reactions appeared more difficult and required increasing both the loading in 1d and the stoichiometry in the nucleophilic component.12 Despite this, only 4ce could be generated with a satisfactory yield (58%). Of note, these samples were contaminated with ca. 10% of the related styrenyl derivatives. Catalyst 1g led to much cleaner processes and 4ce was isolated in pure form in 62% yield. Intriguingly, the initial E/Z ratio evolved from 75:25 to 40:60 indicating an isomerization process had occurred (vide infra). Performing the same experiments at 40 °C delivered (Z)-4ce essentially as a single stereoisomer (E/Z = 04:96). Under the same reaction conditions, (Z)-4o’e was obtained in 73% yield (E/Z = 02:98).13,14 These data suggest that when using [(dmpe)NiCl2] at elevated temperature isomerization is faster than reductive elimination. Similar observations were already documented in seminal contributions from Kumada and coworkers.15 Although there is yet no clear consensus on the exact mechanism(s) which may account for this competing process, the existence of discrete zwitterionic nickel carbene intermediates has been legitimately proposed.16 Alkenyl phosphates. The effect of substitution on the electrophilic component of the nickel-catalyzed crosscoupling was first investigated using vinyl magnesium bromide and substrate (Z)-2p’ - which can be readily prepared as a single stereoisomer starting from 1-(4methoxyphenyl)propan-1-one (See Supporting Information) (Figure 6). Under the optimized reaction conditions for vinyl phosphates, no reaction occurred with [(dppe)NiCl2] 1d. Variations of the stoichiometry, temperature and/or catalyst loading were not effective. In contrast, product formation was indeed observed with [(dmpe)NiCl2] 1g. While at +40 °C, the expected diene (E)4p’a was generated quasi-quantitatively with only partial E/Z isomerization (E/Z = 80:20), at –40 °C (Z)-4p’a was formed as the major stereoisomer (70% yield; E/Z = 16:84) (Figure 6, B). In contrast to observations made with alkenyl Grignard reagent 3e, in this case, isomerization appears slower than reductive elimination at elevated temperatures while it predominates at low temperatures. Quite strikingly, when [(depe)NiCl2] 1h was tested – a precatalyst which only differs from 1g by the nature of the alkyl substituents on the P atoms – almost no reaction and minimal isomerization were observed at –40 °C (10%

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Figure 5. Cross-coupling using alkenyl Grignard reagents (0.25-1.5 mmol scale; alkenyl magnesium bromide: 1.05 equivalents). Isolated yields after column chromatography. In red yields obtained using catalyst 1d. In blue yields obtained using catalyst 1g. (a) 5.0 mol% 1d, 2.10 equiv. of 3e, 0.1 M; (b) 5.0 mol% 1g, 1.05 equiv. of 3e, 0.17 M. sentially no change in the stereoisomeric ratio (see Supporting Information), at –40 °C (E)-2q’ reacted exclusively to produce (Z)-4q’a in 45% yield. The remaining starting

Figure 6. Cross-coupling reactions using alkenyl enol phosphates (Z)-2p’ and either catalyst 1g or 1h (0.5 mmol scale; alkenyl magnesium bromide: 1.05 equivalents). Isolated yields after column chromatography.

Figure 7. Cross-coupling reactions using alkenyl enol phosphates 2q’ and catalyst 1g (0.5-2.0 mmol scale; alkenyl magnesium bromide: 1.05 equivalents). Isolated yields after column chromatography.

yield; E/Z = 80/20). From a practical standpoint, (E)-4p’a could be isolated in 75% yield in pure geometrical form at +40 °C (E/Z = 92:08) using 1h (Figure 6, C-D).

material and the newly generated 1,3-diene were separated by column chromatography enabling to engage geometrically pure (Z)-2q’ in a subse quent catalytic reaction with 1g at +40 °C. Gratifyingly, (E)-4q’a was isolated in 74% yield (33% over 2 steps) in a 85:15 (E/Z) ratio. Overall, these results illustrate that all stereoisomeric crosscoupling products are in principle accessible using catalyst 1g – independently of the stereopurity of the starting alkenyl phosphate.

A phosphate containing only alkyl substituents was evaluated next using nickel complex 1g (Figure 7).17 (E)- 2q’ was cross-coupled successfully at either high or low temperatures without any noticeable isomerization in both cases. A slightly diminished catalytic activity was observed at –40 °C (67% yield (16 h) vs 85% yield (1 h) at +40 °C). As the corresponding (Z) isomer could not be prepared in pure form, we decided to engage instead a 55:45 (E/Z) mixture in the cross-coupling to assess whether this process might be stereospecific or not using 1g. Whereas the reaction conducted at +40 °C afforded 4q’a with es-

To further delineate the scope of the present catalytic method, sterically more demanding enol phosphates 2r’-s’ were surveyed using vinyl magnesium bromide as nucleophilic partner and [(dmpe)NiCl2] as precatalyst (Figure 8).

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afford 2-substituted 1,3-dienes. From a reactivity standpoint this is a remarkable achievement as vinyl crosscoupling partners are notoriously difficult to engage in metal-catalyzed cross-coupling processes. Overall, the two catalytic systems are very practical as they operate under very mild reaction conditions (typically room temperature), at low catalyst loadings (0.1–5.0 mol%), in noticeably short reaction times (typically 1 h or less) and can be scaled up to prepare multi-gram quantities of the products using an ideal stoichiometric amount of each coupling partner. The compatibility of the nickel catalysts with a range of sensitive functional groups and structurally diversified and complex molecular scaffolds has been explored extensively. For particularly sensitive functional groups an operationally simple Negishi variant of the reaction was developed. In this regard, the current protocol not only complements existing methods (i.e enyne crossmetathesis) but offers access to architectures that would be otherwise difficult to synthesize.

Figure 8. Influence of the electronic and steric parameters on the Ni-catalyzed cross-coupling reaction using 1g. (0.5 mmol scale; alkenyl magnesium bromide: 1.05 equivalents). Isolated yields after column chromatography. Thus, (Z)-2r’ could only be cross-coupled successfully at elevated temperature using 5 mol% of 1g, delivering (E)4r’a in 44% yield and with only minimal isomerization (E/Z = 88:12). In contrast, under the same reaction conditions, (Z)-2s’ – where the t-Bu group has been replaced by a trimethylsilyl substituent – gave (Z)-4s’a in 86% yield(E/Z = 08:92).18 The origin of the isomerization in the latter case is unclear but might be tentatively rationalized by the ability of silicon substituents to stabilize negative charges in -position and/or by the substantially longer intermolecular distance C–SiMe3 vs. C–CMe3 (~1.85 Å vs. ~1.54 Å).19 Sensitive phospho-enoate (Z)-2t’ was reacted using the milder Negishi variant of the cross-coupling method (vide supra), leading to complete conversion into 4t’a (E/Z = 88:12) (Figure 8, C). After purification by column chromatography, geometrically pure (Z)-4t’a was isolated in 60% yield. Finally, (E)-4q’b and (E)-4q’c – a particularly congested 1,3-diene – could be prepared in 55% and 65% yield respectively using 1g at +40 °C (Figure 8, D and E).

Extension of this approach to the synthesis of other conjugated 1,3-dienes has been also demonstrated starting from alkenyl Grignard reagents and/or alkenyl enol phosphates. Adjustment of the reaction temperature enabled to access a variety of different olefin isomers with high levels of stereocontrol by capitalizing on a competing isomerization. Current studies in our group aim at understanding the underlying mechanistic features associated with cross-coupling reaction, the isomerization process and the impact of subtle differences in ligand design on the general outcome. Use of 2-substituted 1,3-dienes as a discovery platform for selective catalysis is being investigated.

ASSOCIATED CONTENT Supporting Information. Experimental procedures, characterization of all new compounds and spectral data. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author * Prof. Clément Mazet. University of Geneva, Organic Chemistry Department. Quai Ernest Ansermet 30, Geneva 1211 Switzerland. [email protected]

Notes The authors declare no competing financial interests.

ACKNOWLEDGMENT We thank the University of Geneva and the Swiss Chemical Society (Werner Fellowship to S. F.) for financial support. Ciro Romano is acknowledged for fruitful scientific discussions.

REFERENCES ■ CONCLUSIONS In summary, we have identified two complementary nickel precatalysts for the cross-coupling between vinyl magnesium bromide and a wide variety of vinyl phosphates to

(1) (a) Science of Synthesis; Trost, B. M., Rawal, V. H., Kozmin, S. A., Eds.; Thieme: Stuttgart, Germany, 2009; Vol. 46; (b) De Paolis, M.; Chataigner, I.; Maddaluno, J. Top. Curr. Chem. 2012, 327, 87–146.

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ACS Catalysis (2) For comprehensive reviews on enyne metathesis with ethylene, see: (a) Diver, S. T.; Giessert, A. J. Chem. Rev. 2004, 104, 1317; (b) Hansen, E. C.; Lee, D. Acc. Chem. Res. 2006, 39, 509. For seminal contributions, see: (c) Kinoshita, A.; Sakakibara, N.; Mori, M. J. Am. Chem. Soc. 1997, 119, 12388; (d) Smulik, J. A.; Diver, S. T. Org. Lett. 2000, 2, 2271; (e) Tonogaki, K.; Mori, M. Tetrahedron Lett. 2002, 43, 2235. For the use of sacrificial olefin instaed of ethylene, see: (f) Fustero, S.; Bello, P.; Miró, J.; Simón, A.; del Pozo, C. Chem. Eur. J. 2012, 18, 10991. (3) For seminal contribution for the use of dienyl Grignard reagents derived from chloroprene, see: (a) Aufdermarsh, C. A. J. Org. Chem. 1964, 29, 1994; (b) Nunomoto, S.; Yamashita, Y. J. Org. Chem. 1979, 44, 4788; (c) Nunomoto, S.; Kawakami, Y.; Yamashita, Y. Bull. Chem. Soc. Jpn. 1981, 54, 2831. (4) (a) Cross Conjugation: Modern Dendralene, Radialene and Fulvene Chemistry; Hopf, H.; Sherburn, M. S., Eds. Wiley-VCH: Weinheim, 2016; (b) Sherburn, M. S. Acc. Chem. Res. 2015, 48, 1961. (5) For Ni-catalyzed cross-coupling of dienyl electrophiles, see: (a) Sahlberg, C.; Quader, A.; Claesson, A. Tetrahedron Lett. 1983, 24, 5137; (b) Karlström, A. S. E.; Rönn, M.; Thorarensen, A.; Bäckvall, J.-E. J. Org. Chem. 1998, 63, 2517; (c) Sofia, A.; Karlström, E.; Itami, K.; Bäckvall, J.-E. J. Org. Chem. 1999, 64, 1745. For iron-catalyzed cross-coupling of dienyl phosphates, see: (d) Cahiez, G.; Habiak, V.; Gager, O. Org. Lett. 2008, 10, 2389; (e) Cahiez, G.; Guerret, O.; Moyeux, A.; Dufour, S.; Lefevre, N. Org. Process Res. Dev. 2017, 21, 1542. (6) Li, H.; Fiorito, D.; Mazet, C. ACS Catal. 2017, 7, 1554. (7) For reviews, see: (a) Denmark, S. E; Butler, C. R. Chem. Commun. 2009, 20; (b) Knappke, C. E. I.; von Wangelin, A. J. Chem. Soc. Rev. 2011, 40, 4948. For a rare example of palladium catalyzed cross-coupling between alkenylmagnesium halides with alkenyl electrophiles, see: (c) Gamez, P.; Ariente, C.; Goré, J.; Cazes, B. Tetrahedron 1998, 54, 14825. (8) For reviews on the use of enol phosphates in crosscoupling reactions: (a) Li, B.-J.; Yu, D.-G.; Sun, C.-L.; Shi, Z.-J. Chem. - Eur. J. 2011, 17, 1728; (b) Fuwa, H. Synlett 2011, 1, 6; (c) Sellars, J. D.; Steel, P. G. Chem. Soc. Rev. 2011, 40, 5170. For relevant examples of Kumada cross-coupling reactions with enol phosphates, see: (d) Hayashi, T.; Fujiwa, T.; Okamoto, Y.; Katsuro, Y.; Kumada, M. Synthesis 1981, 1001. (e) Gauthier, D.; Beckendorf, S.; Gøgsig, T. M.; Lindhardt, A. T.; Skrydstrup, T. J. Org. Chem. 2009, 74, 3536. For the use of ketene acetal phosphates in the preparation of cyclic dienes via Pd-catalyzed Stille crosscoupling, see: (f) Nicolaou, K. C.; Shi, G.-Q.; Gärtner, G. P.; Yang, Z. J. Am. Chem. Soc. 1997, 119, 5467. For the use of enol phosphates in the preparation of dienes via Pd-catalyzed Heck reaction, see: (g) Ebran, J.-P.; Hansen, A. L.; Gøgsig, T. M.; Skrydstrup, T. J. Am. Chem. Soc. 2007, 129, 6931. (9) For a comprehensive review on nickel precatalysts in cross-coupling, see: Hazari, N.; Melvin, P. R.; Beromi, M. M. Nat. Rev. Chem. 2017, 1, 1. (10) For reviews on Ni-catalyzed cross-coupling of aryl ethers: (a) Cornella, J.; Zarate, C.; Martin, R. Chem. Soc. Rev. 2014, 43, 8081; (b) Tobisu, M.; Chatani, N. Acc. Chem. Res. 2015, 48, 1717. For Ni-catalyzed cross-coupling with Ar-F, see: (c) Yoshikai, N.; Matsuda, H.; Nakamura, E. J. Am. Chem Soc. 2009, 131, 9590. (d) Liu, X.-W.; Echavarren, J.; Zarate, C.; Martin, R. J. Am. Chem. Soc. 2015, 137, 12470. (11) For Negishi cross-couplings with enolphosphates, see: (a) Wu, J.; Yang, Z. J. Org. Chem. 2001, 66, 7875−7878; (b) Hansen, A. L.; Ebran, J.-P.; Gøgsig, T. M.; Skrydstrup, T. J. Org. Chem. 2007, 72, 6464. (12) 5 mol% of 1g, 2.1 equiv of 3e, 1 h, 0.1 M in THF. (13) Dienes 4o’b-4o’e are homologues of myrcene and some of them have been isolated from natural sources. For 4o’b, see: (a) Brock, N. L.; Ravella, S. R.; Schulz, S.; Dickschat J. S. Angew.

Chem., Int. Ed. 2013, 52, 2100. For 4o’d, see: (b) Nestl, B. M.; Geinitz, C.; Popa, S.; Rizek, S.; Haselbeck, R. J.; Stephen, R.; Noble, M. A.; Fischer, M. P.; Ralph, E. C.; Hau, H. T.; Man, H.; Omar, M.; Turkenburg, J. P.; van Dien, S.; Culler, S. J.; Grogan, G.; Hauer, B. Nat. Chem. Biol. 2017, 13, 275. Diene 4od is a key intermediate in the preparation of the fragrance Georgywood®. For relevant literature, see: (c) Fráter, G.; Müller, U.; Schröder, F. Tetrahedron: Asymmetry 2004, 15, 3967; (d) Hong, S.; Corey, E. J. J. Am. Chem. Soc. 2006, 128, 1346; (e) Barras, J.-P.; Bourdin, B.; Schröder, F. Chimia 2006, 60, 574. (14) Using cyclopropyl magnesium bromide 3f, vinyl cyclopropanes 4bf and 4o’f can be prepared starting from the corresponding vinyl phosphates applying the conditions disclosed on Figure 5 using 1d. The absence of product formation with 1g suggests that subtle mechanistic differences are likely at play with the two catalysts.

For the relevance of vinylcyclopropane 4o’f, see: (a) Schröder, F.; Ruethi, F. WO 2015/059290 A1, April 30, 2015; (b) Schröder, F. WO 2015/059293 A1, April 30, 2015. (15) (a) Tamao, K.; Zembayashi, M.; Kiso, Y.; Kumada, M. J. Organomet. Chem. 1973, 55, c91; (b) Zembayashi, M.; Tamao, K.; Kumada, M. Tetrahedron Letters 1975, 21, 1719; (c) Tamao, K.; Sumitani, K.; Kiso, Y.; Zembayashi, M.; Fujioka, A.; Kodama, S.-I.; Nakajima, I.; Minato, A.; Kumada, M. Bull. Chem. Soc. Jpn. 1976, 49, 1958. (16) (a) Henry, P. M. Acc. Chem. Res. 1973, 6, 16; (b) Huggins, J. M.; Bergman, R. G. J. Am. Chem. Soc. 1981, 103, 3002; (c) Brady, K. A.; Nile, T. J. Organomet. Chem. 1981, 206, 299; (d) Ojima, I.; Clos, N.; Donovan, R. J.; Ingallina, P. Organometallics 1990, 9, 3127; (e) Zargarian, D.; Alper, H. Organometallics 1991, 10, 2914; (f) Murakami, M.; Yoshida, T.; Kawanami, S.; Ito, Y. J. Am. Chem. Soc. 1995, 117, 6408; (g) Amatore, C.; Bensalem, S.; Ghalem, S.; Jutand, A. J. Organomet. Chem. 2004, 689, 4642; (h) Kamijo, S.; Sasaki, Y.; Kanazawa, C.; Schüßeler, T.; Yamamoto, Y. Angew. Chem., Int. Ed. 2005, 44, 7718; (i) Yamamoto, A.; Suginome, M. J. Am. Chem. Soc. 2005, 127, 15706; (j) Krasovskiy, A.; Lipshutz, B. H. Org. Lett. 2011, 13, 3818; (k) Lu, G.-P.; Voigtritter, K. R.; Cai, C.; Lipshutz, B. H. Chem. Commun. 2012, 48, 8661; (l) Lu, G.-P.; Voigtritter, K. R.; Cai, C.; Lipshutz, B. H. J. Org. Chem. 2012, 77, 3700; (m) Daini, M.; Yamamoto, A.; Suginome, M. Asian J. Org. Chem. 2013, 2, 968; (n) Clarke, C.; IncertiPradillos, C. A.; Lam, H. W. J. Am. Chem. Soc. 2016, 138, 8068; (o) Sperger, T.; Le, C. M.; Lautens, M.; Schoenebeck, F. Chem. Sci. 2017, 8, 2914; (p) Yap, C.; Lenagh-Snow, G. M. J.; Karad, S. N.; Lewis, W.; Diorazio, L. J.; Lam, H. W. Angew. Chem. Int. Ed. 2017, 56, 8216. (17) Godenschwager, P. F.; Collum, D. B. J. Am. Chem. Soc. 2008, 130, 8726. (18) (Z)-4s’a: 65% yield (E/Z 01:99) (19) CRC Handbook of Chemistry and Physics, 98th ed.; Rumble, J. R., Ed.; CRC Press: Boca Raton, FL, 2017.

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