NHC-Ni(0) Catalyzed Diastereodivergent Hydroacylative Enyne Cyclization: Synthesis of Heterocycles bearing γ-Enone

Article abstract of DOI:10.1002/adsc.202000718

NHC-Nickel(0) catalyzed 1,3- and 1,4-diastereodivergent hydroacylative heteroenyne cyclization with aldehydes was achieved (Syn-:Anti-, switchable from up to 1:99 to 98:2). Both sets of heterocyclic diastereomers are accessible via this route, with a high

Full text of DOI:10.1002/adsc.202000718

Title: NHC-Ni(0) catalyzed diastereodivergent hydroacylative enyne
cyclization: synthesis of heterocycles bearing γ-enone
Authors: xuefeng yong, Elvis Wang Hei Ng, Zibo Zhen, xiulian lin,
weiwei Gao, and Chun-Yu Ho
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.202000718
Link to VoR: https://doi.org/10.1002/adsc.202000718

Advanced Synthesis & Catalysis
10.1002/adsc.202000718
UPDATE
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
NHC-Ni(0) Catalyzed Diastereodivergent Hydroacylative Enyne
Cyclization: Synthesis of Heterocycles bearing γ-Enone
a, d
d, e
d
d
d
Xuefeng Yong, Elvis Wang Hei Ng, Zibo Zhen, Xiulian Lin, Weiwei Gao and
b,c,d
Chun-Yu Ho*
a
School of Chemistry and Chemical Engineering, Harbin Institute of Technology,Harbin, Heilongjiang, China 150001.
Shenzhen Grubbs Institute, Southern University of Science and Technology (SUSTech), Shenzhen, Guangdong, China
b
5
18055. [E-mail: jasonhcy@sustech.edu.cn]
c
Guangdong Provincial Key Laboratory of Catalysis, Southern University of Science and Technology,Shenzhen,
Guangdong, China 518055.
Department of Chemistry, Southern University of Science and Technology,Shenzhen, Guangdong, China 518055.
d
e
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Repub lic of China
Received: (will be filled in by the editorial staff)
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.
Abstract. NHC-Nickel(0) catalyzed 1,3- and 1,4-
diastereodivergent hydroacylative heteroenyne cyclization
with aldehydes was achieved (Syn-:Anti-, switchable from
up to 1:99 to 98:2). Both sets of heterocyclic diastereomers
are accessible via this route, with a high γ-:-enone
structure ratio. Preliminary DFT investigations indicated
that the manipulation of the N-substituent exerts a direct
the selectivity was largely governed by the sterically
bulky OTBS group on the enyne (Fig. 1b).
[3e, 3f][5]
influence on the diastereoselectivity
of NHC-
nickelacyclopentene formation. The energy differences
associated with the endocyclic bond angle (C-Z-C) changes
noted in the calculations, might possibly account for the
broad scope and high diastereodivergent selectivity
observed.
Keywords: Insertion; Olefination; Acylation; Nickel;
Heterocycles; N-heterocyclic carbenes
Introduction
Multi-substituted
heterocycles
are
commonly
encountered structures that often exhibit important
biological activities and have diverse applications.
Hence, catalytic stereoselective approaches toward
[
1]
heterocycles continue to be extensively researched.
Transition metal-catalyzed cross-cycloaddition and
cyclo-isomerization are powerful techniques whereby
Figure 1. Transition metal-catalyzed hydroacylative enyne
structures. Through the use of aldehydes as reaction cyclization.
partners, highly atom-economical and regioselective

-systems are fused to create various cyclic
[2]
hydroacylative enyne cyclizations have been achieved,
delivering cyclic products with useful enone structures However, its effect on 1,7-oxaenyne diastereoselective
[
3]
hydroacylation was not examined, and a cyclic
template was employed to assist in diastereoselective
(
Fig. 1a, paths a and b). High ees have been achieved
[4]
by utilizing various chiral phosphorus ligands,
however synthesis of multi-substituted heterocycles azacycle formation. The development of a new
hydroacylative strategy that is applicable to the
synthesis of diverse heterocycles and can tolerate both
with high 1,3- and 1,4-diastereoselectivity (d.r.)
remains difficult. For instance, NHC-Ni(0) was found
to be effective in 1,3-syn selective carbocycle small and large substituents for a high d.r. is therefore
synthesis and provided -enones as products, whereby expected to be essential for further advancement in this
1
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
field. Ideally, the strategy should be diastereodivergent, Table 1. Diastereo- and regioselective hydroacylative
[
a,b]
and applicable to the synthesis of both 6- or 7- oxaenyne and azaenyne cyclization.
membered
heterocycles
from
enynes
with
1
,3-relations (Eq. 1)
[
6]
conformationally less restricted spacers.
As part of our continuing efforts on the use of
NHC-Ni as a catalyst for the development of novel
hydroalkenylation methods and gem-olefin synthesis,
we have recently developed a catalytic reductive
hydroalkenylation for the generation of heterocycles,
[
7]
Yield Syn:Anti
1
2
by using hetero-substituted enynes as substrates and 1- entry
R
Z (1)
R = (2) 3
[8]
3 (%)
3
phenylethanol as the terminal reductant.
By
manipulating the N-substitution on enynes, both sets of
diastereoisomers could be obtained with high
selectivity on demand. Preliminary results indicated
that the strategy may also be applicable to simple
azaenyne hydroacylative cyclizations if p-anisaldehyde
is employed instead of a reductant, which offers higher
functionalized heterocycles with γ-enone structures
82
[
d]
[c]
1
4-OMe-Ph (2a) 3aa
9
> 95:5
[
e]
2
0
[
c]
2
3
Ph (2b) 3ab 63 > 95:5
2
-Ph (2c) 3ac 84 > 95:5
[c]
[c]
4-NMe
Ph
O (1a)
4
2-NMe-pyrrolyl (2d) 3ad 80 > 95:5
2-Me-4-OM e-Ph (2e) 3ae 57 > 95:5
2-thiophenyl(2f) 3af 46 > 95:5
[
[
c]
c]
(
Scheme 1). However, the reasons for these similarities
5
and high selectivities remain unclear. In this regard,
herein we report our recent efforts on the
6
[
f,g]
[c]
diastereoselective
hydroacylative
synthesis
of
7
4-F-Ph (2g) 3ag 90 > 95:5
tBu (2h) 3ah 62 92:8
3ba 90 > 95:5
heterocycles. We envisage the provision of versatile
acyl side chains for further transformations and
valuable carbon frameworks via this strategy,
improving on previously reported reductive
hydroalkenylations. Additionally, through DFT
calculations, we hope to offer new insights that are
8
[
c]
9
O (1b)
NH (1c)
[
h]
10
3ca 74 98:2
Me
Ph
4-OMe-Ph (2a)
1
1
1
2
NMs (1d)
NTs (1i)
NH (1e)
3da 92 11:89
3ia 89 36:64
beneficial
to
rationalizing
diastereodivergent
[
i]
[c]
transformations.
13
3eh 59 >95:5
tBu (2h)
1
1
1
1
4
5
6
7
NMs (1f)
NMs (1f)
NTs (1h)
3fh 90
9:91
[
j,k]
3fa 98 4:96
4
-OMe-Ph (2a)
3ha 92 34:66
[
j]
p-Anisyl O(1g)
4-OMe-Ph (2a) 3ga 93 >95:5
1
,4-relations (Eq. 2)
Yield Syn:Anti
1
2
entry
18
R
Z (1)
R = (2) 3
3
(%)
3
Scheme 1. Our preliminary results on diastereodivergent
hydroacylative cyclization of simple azaenynes[8]
Ph
O (1a)
O (1b)
3aa 61
6:94
4
-OMe-Ph (2a)
1
2
2
2
9
0
1
2
Me
3ba 55 14:86
3ca 58 9:91
NH (1c)
NMs (1d)
NH (1e)
Results and Discussion
Me
Ph
4-OMe-Ph (2a)
tBu (2h)
[
c]
3da 81 > 95:5
Optimization of selective -enone synthesis
[c]
3eh 79 <5:95
3fh 61 90:10
We commenced our investigation by reacting -
substituted 1,7-oxaenyne 1a and aldehyde 2, using the
IPr-Ni(0) catalyst in toluene at r.t. (Table 1, Eq. 1). To
our delight, the desired oxaenyne hydroacylative
cyclization was successful, yielding pyrans with high
23
[a]
NMs (1f)
0
.5 mmol 1 or 1 and 0.75 mmol 2 in 1 mL toluene
was gradually added to 0.05 mmol NHC-Ni(0) catalyst in 2
mL toluene at 2 mL/hr, and the mixture was stirred at r.t. for
[b]
3
h before work up.
Products are shown in relative

-enone structure ratios and excellent 1,3-d.r.s for
the first time (entries 1 – 8, 3aa – 3ah, and 1,3-syn-
anti- 95:5). Electron-rich aldehydes were
[c]
configurations. Minor stereoisomer was not observed in
the H NMR spectra, and was not separable/ detected in
GCMS. IMes was used. 20 mol% Ni, Ni:PCy3 = 1:2.
1
:
>
[d]
[e]
[f]
advantageous for competing with several other
undesired, yet commonly observed, reactivities of
[g]
2
[h]
20 mol% catalyst, 1a:2g = 1:1.2. R = 4-CF3-Ph failed.
2
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
By GCMS. Ran at 0.04 M of 1e. [j] Structure determined
[
i]
Second, in addition to being applicable to enynes
with propargyl-Z, the above-discussed strategy was
also valid for enynes with allyl-Z (Set B), as
exemplified in Table 1 Eq. 2. This finding
[k]
by XRD. Data collected from ref. 8.
[9]
structurally flexible terminal enynes. Possible side complements the above 1,3-diastereodivergent
[10]
reactions, including alkyne oligomerization,
synthesis by offering access to structurally analogous
homo-dimerization and heterocycles with well-defined 1,2,4-skipped
[13]
[
11]
[12]
aldehyde,
or enyne
alkene or alkyne hydroacylation, were all inhibited stereocenter substitution patterns. Third, in addition to
in the absence of gem-substitution assistance (use of its applicability to acyclic 1,7-enynes, the method was
-R has a limited impact on the 1,7-enyne found to be practical for cyclic enynes and 1,8-enynes
conformation (discussed later).
1

(Table 2, Sets C and D). Although a higher catalyst
1
Notably, the use of significantly smaller R vs. Ph loading was required for hetero-cycloheptene synthesis,
likewise delivered high 1,3-syn-:anti- d.r.s under the the diastereodivergent synthetic efficiency was
same conditions (entries 1 and 9), indicating that the nonetheless remarkable considering these challenging
1
size of R is not the most critical factor in determining examples. The preferred relative configuration of 1,8-
the d.r. Moreover, a high d.r. was also observed when enyne stereocenters was directed again by Z, however
smaller ligands were employed (entry 1, IPr vs. IMes it was opposite to that observed for 1,7-enynes.
3
and PCy ). Although the yield was lowered
In summary, the hydroacylative cyclizations
dramatically, such a comparison clearly indicated that generally proceeded with high yields and exhibited a
[14]
the high d.r. was not controlled by the ligand size. In broad scope. The exocyclic gem-olefin was found to
addition, when 1 was used instead of 1 (Fig. 1c, allyl- be stable under mild hydroacylative cyclization
vs. propargyl-Z), the synthesis of pyrans with high 1,4- conditions. No further hydroacylation, isomerization or
anti-:syn- d.r.s and high γ-:-enone structure ratios carbonyl-ene reactions were noted by NMR
was accomplished (Table 1, Eq. 2, entries 18-19). The spectroscopy, hence a versatile handle is provided for
1
new stereocenter formed at C4 is further away from R
subsequent manipulations and for generating new
than in the 1,3- heterocycles, suggesting that the highly stereocenters. In addition, the high γ-:-enone ratio,
diastereoselective synthesis was not a direct result of high d.r., and the diastereodivergent selectivity trend
minimizing the steric repulsion between R and ligand were well-preserved in all the cases examined. This
1
substituents.
generality highlighted the competitiveness and unique
Azaenynes with Z = NH provided similar results to advantage of our strategy for preparing highly
the corresponding oxaenynes in the synthesis of both substituted heterocycles, which avoids catalyst
1
,3- and 1,4-diastereomers (entries 9 and 10, 19, and redesign and synthetic route revision for the generation
2
0). More interestingly, inverse diastereoselectivity of the opposite isomer.
was observed when Z = NMs (entries 11, 14, 15, 21,
Rationale for diastereodivergence
and 23). This outcome appears to be common for a
1
2
variety of R and R , as it was observed for both
Although Z could possibly affect the enyne
aromatic and aliphatic substituents (entries 11 and 15; conformational preference, conformational analysis of
entries 14 and 15). However, the use of a bulkier 1c and 1d via DFT calculations suggested that the
sulfonyl group (NTs vs. NMs) caused a dramatic drop enynes remain very flexible and do not display a single
in d.r. (entry 11 vs. 12; 15 vs. 16), which is unexpected dominant conformation irrespective of Z, implying that
in view of the steric considerations and thus deserves the diastereodivergence did not arise from a
[
15]
further investigation (see later DFT calculations).
conformational constraint on the enyne.
While the
could possibly
explain the axial preference of -Me with NMs enynes
[16]
prevailing 1,3-allylic strain model
Substrate scope ofheteroenynes for γ-enones
Next, the substituent effect of the hetero-substituted and therefore the d.r. switch, the lower d.r.s observed
enynes on this hydroacylative enyne cyclization was with sterically bulkier NTs compared to NMs cases, as
studied under our standard conditions using IPr-Ni(0) noted in Table 1 (entry 11 vs. 12, and 15 vs. 16), were
as a catalyst at r.t. (Table 2). First, the size of the - intriguing and led us to pursue a new model,
1
substituent (R ) and the effects of the -substituent supplementary to the explanation based on the 1,3-
were evaluated (Set A). The results indicated that not allylic strain.
only phenyl, but also cyclic and linear alkyl chains can
Given that comparable d.r.s were obtained
be utilized to provide the desired reactivity and irrespective of the partners employed (alcohol or
selectivity (high γ-:-enone ratio, high d.r., and a aldehyde), we reasoned that the effective inversion of
reliable trend in diastereodivergent selectivity). diastereoselectivity was determined solely by the
Moreover, both syn- and anti-substituents at the - nickelacyclopentene intermediate. This is supported by
position were tolerated, which allows for a general DFT calculations of the relative stability of syn- and
strategy for the assembly of well-defined 1,2,3- anti-nickelacyclopentene
intermediates with
a
[
17]
contagious stereocenters with high selectivity in 6- simplified NHC (Table 3),
which successfully
membered heterocycles bearing a γ-enone.
predicted the inversion of diastereoselectivity with a
different Z in both propargyl and allyl heteroenynes
3
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
1
(
Fig. 1c, Eq. 1 and 2). Whereas O or NH enynes favor angle (Fig. 2a). In addition, -R can also affect the
1
1
intermediates with equatorial -R (Me), NMs enynes nearby endocyclic angle (Fig. 2b), with axial R
1
favor intermediates with axial -R (Me).
increasing the angle to a larger extent, presumably to
We reasoned that the slight difference in the reduce undesired 1,3-diaxial interactions. Thus, we
1
hybridization of N in Z could modify the natural propose that for NMs enynes, axial -R will reinforce
preference of the endocyclic C-Z-C angle (Fig. 2a). As the expansion of the endocyclic angle and is hence
the N lone pair becomes more delocalized, the p- favored over the alternative intermediate with
1
character of the lone pair increases and the p-character equatorial -R . In contrast, for O and NH enynes,
of the N-C orbital decreases correspondingly, leading which prefer a smaller endocyclic angle, intermediates
1
to a preference for expanding the endocyclic C-Z-C with equatorial -R are favored.
Table 2.Heteroenyne scope for diastereodivergent hydroacylative cyclizations with aldehydes.[a], [b]
[
a]
[b]
Standard procedure was followed. Enyne and cyclization products are shown in relative configurations. Yields refer to the
[
c]
major stereoisomer only, and the syn-:anti-selectivity is shown in parenthesis. Minor stereoisomer was not observed in NMR,
and was not separable/ detected in GCMS. [d] By GCMS. 20 mol% catalyst. Structure determined by XRD.
[e]
[f]
4
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
Table 3. Relative stabilities of NHC-nickelacyclopentene 1.5° by axial-Me, the meta-endocyclic angle is
intermediates from -methyl heteroenynes 1b, 1c, 1d and decreased only by 0.1°, which is practically negligible.
1
b, 1c, 1d.
Correlation of the bond angle changes according to -
substitution and Z, therefore, implies their significantly
higher impact on the d.r., compared to that of the -
position, and hence the stereochemistry at the -
position has a relatively small effect on the
diastereoselectivity. Based on DFT calculations and
analysis of the endocyclic C-Z-C angle, a proposed
catalytic cycle and mechanism for Z-directed 1,3- and
1
,3-Syn, Anti
1,3-Syn:Anti
entry Z
Rel. G
kcal/mol)
[
b]
Hydroacylative Reductive
[
a]
(
1,4-diatereodivergent
cyclizations are presented in Figure 5. First, the
selected choices of and enyne direct an
intramolecular diastereodivergent enyne oxidative
hydroacylative
enyne
[3f]
1
2
3
O
NH
NMs
0, +2.9
0, +2.3
+3.0, 0
95:5
98:2
95:5
95:5
Z
11:89
12:88
[
20]
cyclization with NHC-Ni(0) as discussed above.
3
Subsequent aldehyde insertion to the Ni-Csp center
gives the corresponding oxanickelacycloheptenes.
Finally, typical -H elimination followed by reductive
elimination of H and alkenyl groups on Ni provides the
desired products and regenerates the catalyst.
1
,4-Syn, Anti
1,4-Syn:Anti
Hydroacylative Reductive
entry Z
Rel. G
[b]
[
a]
(
kcal/mol)
+2.2, 0
+1.7, 0
0, +3.7
4
5
6
O
NH
NMs
14:86
9:91
11:89
3:97
96:4
94:6
[
a]
Level of theory: SMD(toluene)-B3LYP-D3(BJ)/def2-
TZVPP//B3LYP-D3(BJ)/6-31G*-SDD.[18]
[b]
Data were
collected from hydroalkenylation products in ref. 8.
Figure 3. Endocyclic C-Z-C angle for the NHC-
[
a]
nickelacyclopentene intermediates.
[
a]
The more stable intermediate is denoted in bold. From
DFT calculations at SMD(toluene)-B3LYP-D3(BJ)/def2-
Figure 2. Effect of Z and -R on the C-Z-C angle. a)
Endocyclic C-Z-C angle and hybridization of the Z-centered
orbital that is engaged in endocyclic Z-C bond formation
[18]
TZVPP//B3LYP-D3(BJ)/6-31G*-SDD(Ni).
[19]
(from NBO analysis
at B3LYP-D3(BJ)/6-31G*). b)
Effect of axial and equatorial Me on the endocyclic angle.
Indeed, the endocyclic C-Z-C angles of the
nickelacyclopentene
intermediate
from
DFT
calculations appear to be consistent with the above
proposal (Fig. 3). For Z = O or NH, the intermediate
with a smaller C-Z-C angle is favored, as it is closer to
the natural preference of the C-Z-C angle and
additionally minimizes 1,3-diaxial interactions. For Z
=
NMs, the intermediate with a larger C-N-C angle is
favored, as it better accommodates the higher p-
character of N. In fact, the X-ray structures of the
cyclization products indicated a large C-Z-C angle for
3
fa with Z = NMs (114.7°) and a small C-Z-C angle
for 3ga with Z = O (111.5°) (Fig. 4). Furthermore, the
1
endocyclic angle widening effect of the -R group
diminishes rapidly with distance; whereas the ortho-
endocyclic angle in methylcyclohexane is increased by
Figure 4. X-ray structures of the cyclization products and
DFT structures ofNHC-nickelacyclopentene intermediates.
5
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
Figure 5. Proposed mechanism for the NHC-Ni(0)-catalyzed diastereodivergent hydroacylative enyne cyclization: a)
,3-relations. b) 1,4-relations.
1
Conclusion
insertion with aldehyde, and -bond metathesis with
alcohol), it could serve as a key intermediate for
related developments with other coupling partners. In
practice, the method is also operationally simple, with
a single catalyst being used for a broad range of
heterocycle diastereodivergent syntheses. Overall, the
strategy is expected to have broad potential
applications in other metalacyclopentene-associated
cyclizations. Investigations into the utility of this
In summary, NHC-Ni(0) catalyzed highly
diastereodivergent and regioselective hydroacylative
1
,n-heteroenyne cyclizations with aldehydes were
achieved. The choice of hetero-substituents on the
enyne and that of –systems (n = 7, 8, switchable
from 98:2 to 1:99), provides access to diverse densely
substituted heterocycles bearing γ-enone structures. discovery are currently underway.
The success of the diastereodivergent synthesis is
attributed to the selective formation of a more stable
nickelacyclopentene intermediate, revealed with the Experimental Section
aid of DFT calculations at this stage, whose stability
is strongly affected by the NBO of the nickelacycle
and the Z of the selected enone. This feature was
found to be highly competitive in terms of changes in
energy levels; hence, the methodology could tolerate
diverse enyne substitution patterns with variable R
sizes and can be implemented for the assembly of
contagious and skipped stereocenters on demand.
Moreover, as it operates independently of the ensuing
intermolecular bond formation events (e.g. carbonyl
Standard Procedure: A solution of 1 and 2 in 1 mL
toluene was added to a catalyst mixture of IPr and Ni(cod)2
in 2 mL toluene (0.05 mmol, 10 mol% each) at 2 mL/h.
After stirring for 3 h at r.t. and workup, the d.r.s and yields
1
were determined by crude H NMR spectroscopy and
isolation. The relative configurations of the major products
were determined by NOESY and by comparison with the
isomers obtained by other Z groups (see SI for details).
6
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
All DFT calculations were carried out at SMD(toluene)-
B3LYP-D3(BJ)/def2-TZVPP//B3LYP-D3(BJ)/6-31G*-
Ed. 2008, 47, 1312-1316; c) T. Suda, K. Noguchi, K.
Tanaka, Angew. Chem. Int. Ed. 2011, 50, 4475-4479.
[5] γ-enone was obtained in one case in ref 3f for
carbocycle synthesis in 57% yield, and no
diastereoselective version was examined.
[6] Recent reviews: a) S. Krautwald, E. M. Carreira, J. Am.
Chem. Soc. 2017, 139, 5627-5639; b) L. Lin, X. Feng,
Chem. Eur. J. 2017, 23, 6464-6482; c) I. P. Beletskaya,
C. Nájera, M. Yus, Chem. Rev. 2018, 118, 5080–5200;
d) C. Nájera, F. Foubelo, J. M. Sansano, M. Yus, Org.
Biomol. Chem. 2020, 18, 1279-1336; Recent examples:
d) S. Singha, E. Serrano, S. Mondal, C. G. Daniliuc, F.
Glorius, Nat. Cat. 2020, 3, 48-54; e) X. Wu, Z. Chen,
Y.-B. Bai, V. M. Dong, J. Am. Chem. Soc. 2016, 138,
12013-12016; f) organocatalysis: M. Bihani, J. C. G.
Zhao, Adv. Synth. Catal. 2017, 359, 534-575.
[18]
SDD(Ni) level of theory
using the Gaussian 16 program
[
21]
[19a]
package, and hybridization
was analyzed with NBO
[
19b]
7
.0 program
(see SI for details).
X-Ray Crystallographic Data: CCDC-1972921 (3ga),
972922 (3fa), 1972925 (3ua), 1972924 (3ra), and
1
1
972923 (3xa) contain the supplementary crystallographic
data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements
CYH thanks Shenzhen Nobel Prize Scientists Laboratory Project
(
C17783101), SZ research fund (JCYJ 20170817105041557),
Guangdong Provincial Key Laboratory of Catalysis
2020B121201002), and SUSTech (50/Y01506014). ENWH
(
[
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7
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
diastereoselectivity was invariably observed regardless
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8
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Advanced Synthesis & Catalysis
10.1002/adsc.202000718
UPDATE
NHC-Ni(0)
Catalyzed
Diastereodivergent
Hydroacylative Enyne Cyclization: Synthesis of
Heterocycles bearing γ-Enone.
Adv. Synth. Catal. Year, Volume, Page – Page
Xuefeng Yong, Elvis Wang Hei Ng, Zibo Zhen,
Xiulian Lin, Weiwei Gaoand Chun-Yu Ho*
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