Metal-Free Oxidative Decarbonylative [3+2] Annulation of Terminal Alkynes with Tertiary Alkyl Aldehydes toward Cyclopentenes

Article abstract of DOI:10.1021/acs.joc.8b01130

A new metal-free oxidative decarbonylative [3+2] annulation of terminal alkynes with tertiary alkyl aldehydes is presented, which features broad substrate scope and excellent selectivity. The selectivity of this reaction toward cyclopentenes and indenes relies on the nature of the aldehyde substrates. While treatment of tertiary γ,δ-unsaturated aldehydes with common terminal alkynes assembles cyclopentenes, 2-methyl-2-arylpropanals succeed in accessing indenes.

Full text of DOI:10.1021/acs.joc.8b01130

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Article
Metal-Free Oxidative Decarbonylative [3+2] Annulation of Terminal
Alkynes with Tertiary Alkyl Aldehydes Toward Cyclopentenes
Hua-Xu Zou, Yang Li, Xu-Heng Yang, Jiannan Xiang, and Jin-Heng Li
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b01130 • Publication Date (Web): 05 Jun 2018
Downloaded from http://pubs.acs.org on June 6, 2018
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Page 1 of 28
The Journal of Organic Chemistry
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Metal-Free Oxidative Decarbonylative [3+2]
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Annulation of Terminal Alkynes with Tertiary Alkyl
Aldehydes Toward Cyclopentenes
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Hua-Xu Zou,†,‡ Yang Li,*†,‡ Xu-Heng Yang,†,‡ Jiannan Xiang† and Jin-Heng Li*,†,‡,§
†State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha
410082, China
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‡Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle,
Nanchang Hangkong University, Nanchang 330063, China
§State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
liyang8825490@126.com and jhli@hnu.edu.cn
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required
according to the journal that you are submitting your paper to)
R4
H
R4
R1
R1
R1
R1
R3
R2
R3
R2
TBHP, PhCl, 100 o
TBHP, PhCl, 100 o
C
C
R3
OHC
R2
R3
R2
OHC
metal-free oxidative [3+2] annulation
28 examples, up to 81% yield
Abstract
A new metal-free oxidative decarbonylative [3+2] annulation of terminal alkynes with tertiary
alkyl aldehydes is presented, which features broad substrate scope and excellent selectivity. The
selectivity of this reaction toward cyclopentenes and indenes relies on the nature of the aldehyde
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substrates: while treatment of tertiary γ,δ-unsaturated aldehydesd with common terminal alkynes
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assemble cyclopentenes, 2-methyl-2-arylpropanals succed to access indenes.
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Introduction
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Five-membered carbocycles, including cyclopentenes and indenes, are important structural motifs
which widely existed in natural products and pharmaceuticals (Figure 1).1,2 In particular,
cyclopentenes and their polycycles, such as carbovir,2a 4-ACPCA,2b gukulenin A/B,2c taiwaniaquinol
D,2f and ()-japonicols C,2g exhibit significant biological activities, as well as are versatile
intermediates for the synthesis of natural products, bioactive compounds, functional materials and
significant chiral ligands.1 Accordingly, construction of such cyclopentene backbones continues to
be a major focus of chemical synthesis, and conventional synthetic methodologies are concentrated
on reactions that involve intra- or intermolecular annulation processes.1,3,4 Despite impressive
advances in the field, efficient intermolecular approaches to selectively access cyclopentene
structures, especially structures that own an all-carbon quaternary center, is challenging3 and
examples of radical-mediated annulation for such purposes are quite rare.4 Recently, remarkable
progress in the oxidative radical catalysis that has been developed for the intramolecular annulation
of unsaturated molecules (e.g. alkynes and alkenes) initiated by the alkyl carbon-centered radical
systems;5 however, there has been no corresponding
Figure 1. Important molecules containing five-membered carbocycle moieties
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The Journal of Organic Chemistry
N
NH2
OH
OH
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2
3
4
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8
O
N
OH
O
HO
HO
O
NH
NH2
N
COOH
4-ACPCA
H
iPr
H
iPr
R
Carbovir
Ph
AcO
OH
O
HO
2C
Gukulenin A (R = CHO)
Gukulenin B (R = CH2OH)
HO
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H
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N
OH
CHO
iPr
OH
O
H
N
O
MeO
(A chemokine
receptor modulator)
(Aldosterone
synthase inhibitors)
OH
Taiwaniaquinol D
(±) - Japonicols C
success with intermolecular annulation reactions, wherein the intramolecular version is usually
preferential. We envisioned that the alkyl carbon-centered radical systems having a radical-
accepted functional group could be used to competitively trap the radical intermediate from their
initial reaction with unsaturated molecules and consequently the intramolecular process might be
suppressed.
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Very recently, Tang group4g and our group4h independently developed new strategies, including
the classical Cu-catalyzed halogen atom transfer strategy and the Ag-catalyzed oxidative
decarboxylation strategy, for the synthesis of cyclopentenes via metal-catalyzed [3+2] annulations
of terminal alkynes with unsaturated α‑halogenocarbonyls or tertiary unsaturated acids (eq 1;
Scheme 1a). In 2016, we developed a new metal-free radical-mediated oxidative decarbonylative
hydroalkylation of terminal and internal alkynes with alkyl aldehydes, including benzyl, secondary
and tertiary alkyl aldehydes using di-tert-butyl peroxide (DTBP) oxidant, which enables the
simultaneous formation of a C-C bond and a C-H bond through a sequence of decarbonylation,
radical addition and protonation (eq 2; Scheme 1b). Subsequently, we have reported a manganese-
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catalyzed intermolecular oxidative acylative annulation of alkynes with -vinyl aldehydes for the
divergent synthesis of bridged tricarbocycles, bridged bicyclic and tricyclic carbocycles. This
reaction is applicabe to secondary γ,δ-vinyl aldehydes, thus three chemical bonds, including two C-
C bonds and one C-H bond, are formed via aldehyde C(sp2)-H oxidative functionalization, [4+2]
annulation and protonation cascades (eq 3; Scheme 1b). However, Using and a tertiary γ,δ-vinyl
aldehyde the reaction proceeded via a decarbonylative [3+2] annulation process. On the basis,
aldehydes can undergo decabonylation and acylation selevtively, which rely on the electronic and
steric hindrance nature of steraldehyes as well as the oxidative reaction conditions.
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As a continuous interst in the oxidative tansformations of aldehydes with unsaturated
hydrocarbons, we here report a new metal-free oxidative decarbonylative [3+2] annulation of
terminal alkynes with tertiary alkyl aldehydes for the synthesis of diverse polysubstituted
cyclopentenes. This reaction allows the formation of two C-C bonds through a sequence of
decarbonylation6,7, annulation and protonation, and represents the first example of intermolecular
[3+2] annulation of terminal alkynes using an oxidative radical-mediated decarbonylation strategy.
Furthermore, this reaction could be extended to access indenes involving aryl C(sp2)-H
functionalization by designing the substrates (eq 4; Scheme 1c).
Scheme 1. Radical-mediated [3+2] annulation and transformation of aldehydes.
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The Journal of Organic Chemistry
Metal-catalyzed annulation
a) Previous work:
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i) Classical halogen atom transfer
ii) Oxidative decarboxylation
R2 R3
H
R2 R3
X
X
R1
R1
H
CO2
n
R1
(1)
n
CuSO
S2O8
, K2
4, bpy,
AgNO3
1
R3
2CO
, R3
oC
2O/MeCN, 40 oC
H
R3
X = Cl, Br, I R2
, MeCN, 80
=3ester, ketone
R2
R2
K
= alkyl
n = 1, 2
R2
, R3
Oxidative radical transformations of aldehydes
9
b) Our previous work:
R2
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DTBP
+
R1
R2
OHC R3
(2)
(3)
MeCN, 110 o
C, 12 h
= 1o (only benzyl), 2
alkyl
R3
R1
R1
R2
o, 3o
R3
H
H
(10 mol %)
R1
MnSO4
TBHP (3 equiv)
H
R1
R2
+
+
3, Ar, 100 o
R'
PhCF
C, 12 h
O
R
= aryl, alkyl, TMS, CO
= H, Ph, CO
R1
R2
2Me, CON(Me)Ph
tertiary aldehyde
O
secondary
aldehydes
(only two examples)
2Me, CONMe2
Metal-free oxidative decebonylative annulation
R4
c) This work:
R4
R1
Metal-Free
R3
R1
+
(4)
TBHP, PhCl, 100 o
C, Ar, 12 h
1
R3
R2
R2
OHC
2
3
Results and discussion
We initiated our investigations of the [3+2] annulation by combining phenylacetylene (1a) with
2,2-dimethylpent-4-enal (2a) in the presence of oxidants (Table 1). After evaluating various
reaction parameters, alkyne 1a reacted with 2,2-dimethylpent-4-enal (2a), and 3 equiv of TBHP
o
(tert-butyl hydroperoxide; 5 M in decane) in PhCl at 100 C for 12 h was preferred and gave the
desired cyclopentene 3aa in 74% yield (entry 1). However, the reaction could not occur in the
absence of TBHP (entry 2). Other alternative oxidants, such as aqueous TBHP, DTBP (Di-tert-butyl
peroxide), TBPB (tert-Butyl peroxybenzoate), CHP (Cumene hydroperoxide) and K
2
S
2
O , displayed
8
reactivity (entries 3-7), but they were inferior to TBHP (5 M in decane). We found that a lower
amount of TBHP (2 equiv) had a negative effect (entry 8), and a higher amount of TBHP (4 equiv)
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delivered identical results to those of 3 equiv TBHP (entry 9). A screen of the solvent effect
revealed that the use of CH ClCH Cl resulted in no formation of 3aa (entry 10), and two other
1
2
3
4
2
2
5
6
solvents, including MeCN and DMF, exhibited less efficient than PhCl (entries 11 and 12). Among
7
8
9
o
the reaction temperature effect examined, the reaction at 100 C was turned out to be taken
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precedence over either 110 oC or 90 oC (entry 1 versus entries 13 and 14). It is noteworthy that the
reaction is applicable to 1 mmol scale of alkyne 2a, accessing 3aa in good yield (entry 15).
Table 1. Screening of the reaction conditionsa
Ph
Ph
TBHP (3 equiv)
PhCl, 100 o
+
C, Ar, 12 h
OHC
2a
1a
3aa
Entry
1
variation from the standard conditions
Yield [%]b
none
without TBHP
74
0
2
26
48
36
51
14
52
72
trace
62
49
73
58
70
3
4
5
6
7
8
9
TBHP (70% in H O)
2
DTBP instead of TBHP
TBPB instead of TBHP
CHP instead of TBHP
K
2
S2
O8 instead of TBHP
TBHP (2 equiv)
TBHP (4 equiv)
10
11
12
13
14
CH
2
ClCH Cl instead of PhCl
2
MeCN instead of PhCl
DMF instead of PhCl
110 oC
90 oC
none
15b
a
Reaction conditions: 1a (0.2 mmol), 2a (2 equiv), TBHP (5 M in
decane; 3 equiv), PhCl (2 mL), argon, 100 oC and 12 h. b 1a (1 mmol),
PhCl (5 mL) and 36 h.
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The Journal of Organic Chemistry
Having established the optimal reaction conditions, we turned our attention to exploit the scope
1
2
3
of this [3+2] annulation with regard to alkynes 1 and aldehydes 2 (Table 2, Scheme 2 and Scheme
3). In the presence of 2,2-dimethylpent-4-enal (2a), a wide range of electron-rich and electron-
deficient terminal alkynes 1b-p were found to be compatible with the optimal conditions (3ba-pa;
Table 2). For aryl alkynes 1b-h, various substituents, including Me, MeO, Br and Cl, on the aryl
moiety were well tolerated (3ba-ha). It was noted that the substitution electronic nature had a
fundamental influence on the reactivity, but the substitution position showed slight effect. While
aryl alkyne 1b having an electron-donating p-Me group delivered 3ba in 81% yield, aryl alkyne 1d
with a weak electron-withdrawing position were converted into 3ea-ga, respectively, in 66% yield.
It was noted that 1-ethynylnaphthalene 1i was transformed into 7,7a,8,9-tetrahydrocyclopenta-
[a]phenalene (3ia), a cyclopentene-fused polycycle, via oxidative decarbonylation, annulation,
protonation and C-H functionalization cascades. Heteroaryl alkynes 1j-k were both viable for
giving 3ja-ka in good yields. Two functionalized alkynes, including vinyl alkyne 1l and 1,3-diyne
1m, were viable to furnish functionalized cyclopentenes 3la and 3ma, which made this [3+2]
annulation more attractive. Unfortunately, aliphatic alkyne 1n had no reactivity (3na). For
electron-deficient alkynes, namely 1-phenylprop-2-yn-1-one 1o, benzyl propiolate 1s and N-
methyl-N-phenylpropiolamide 1p, were suitable substrates (3oa-pa). Notably, propiolamide 1p gave
3pa in moderate yield along with an inherent C-H functionalization product 4pa. It was noted that
internal alkyne 1q was not a suitable substrate (3qa).
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The feasibility of the [3+2] annulation with other alkyl aldehydes 2b-g was next investigated
(3ab-ad, 3je, and 3af-ag). Using tertiary alkyl aldehydes, such as 2,2-diethylpent-4-enal (2b), 2-
ethyl-2-methylpent-4-enal (2c), 2,2-diethylhex-4-enal 2d and 2-methyl-2-phenylpent-4-enal 2e,
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react with alkynes 1a or 1j efficiently, affording the corresponding products 3ab-3ad and 3je in
moderate yields. However, secondary alkyl aldehyde 1f was inert and could be recovered (3af).
Furthermore, attempt to build six-membered ring from 2,2-dimethylhex-5-enal (2g) was failed
(3ag).
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Table 2. Variations of the terminal alkynes (1) and -vinyl alkyl aldehydes (2)a
R4
R4
H
TBHP
PhCl, 100 o
Ph
R1
+
R3
R2
C, Ar, 12 h
1
OHC
R3
R2
2
3
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The Journal of Organic Chemistry
Br
Cl
MeO
1
2
3
4
5
6
7
8
H
H
H
H
H
3da
, 60%
MeO
3ea
3ba
, 81%
, 72%
3ca
, 68%
H
H
9
Cl
N
Cl
10
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12
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46
MeO
, 78%
3ga
S
3ha
, 66%
3ia
, 46%
3fa
, 70%
Ph
H
H
H
H
H
3ka
, 65%
3ma
, 72%
3la
, 41%
, 57%
O
3ja
O
H
H
Ph
N
+
N
Ph
O
3na
, trace
3oa
, 46%
, 47%
, 21%
4pa
3pa
H
H
H
H
Ph
Ph
Ph
Ph
Ph
3ad
, 51%
3ab
3ac
, 58%
, trace
, 65% (d.r. = 1:1)
3qa
H
H
H
Ph
Ph
Ph
, 37% (d.r. = 1:1)
N
3ag
3af
, trace
, trace
3je
a Reaction conditions: 1 (0.2 mmol), 2 (2 equiv), TBHP (5 M in decane; 3 equiv),
PhCl (2 mL), argon, 100 oC and 12 h.
Importantly, this reaction was applicable to 2-methyl-2-phenylpropanal (2h). In the presence of
TBHP, 2-methyl-2-phenylpropanal (2h) could smoothly undergo the [3+2] annulation through C-H
functionalization to assemble indenes 3jh and 3ph. However, secondary 2-phenylpropanal 2i failed
to execute the reaction under the optimal conditions (3ji).
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Scheme 2. The decarbonylation annulation with 2-phenylpropanals (2)
1
2
3
4
R4
5
6
7
8
TBHP
Ph
R1
H
+
R3
R2
PhCl, 100 o
C, Ar, 12 h
1
OHC
R3
2
R2
3
9
10
11
12
13
14
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60
O
Ph
N
N
N
, 52%
, 51% (d.r. = 2:1)
, trace
3ji
3jh
3ph
As shown in Scheme 3, treatment of alkyne 1a with pivalaldehyde 2j and TBHP afforded the
hydroalkylation product 5aj in 70% yield (eq 5).6j For 2-phenylacetaldehyde 2k, a primary
aldehyde, decarbonylative hydroalkylation of 4-ethynyltoluene (1b) also occurred, offering the
alkene 5bk in 40% yield (eq 6). However, the reaction of alkyne 1a with aldehyde 2a was inhibited
when a stoichiometric amount of radical inhibitors, including TEMPO, hydroquinone and 2,6-di-
tert-butyl-4-methylphenol (BHT), was added (eq 7). These results suggest that this [3+2] annulation
reaction involves a free-radical process. To further understand the mechanism, the deuterium
labeling experiments were performed (eqs 8 and 9). In the presence of D
atoms were incorporated into the resulting product 3aa (eq 8). However, no deuterium-labelled
product was observed when using CD CN as the medium (eq 9).
2
O, a number of deuterium
3
Scheme 3. Other aldehydes and control experiments
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The Journal of Organic Chemistry
H
1
2
3
4
TBHP (3 equiv)
+
OHC
2j
Ph
(5)
(6)
PhCl, 100 o
C, Ar, 12 h
1a
Ph
5aj
, 70%
H
5
6
7
8
TBHP (3 equiv)
PhCl, 100 o
+
Ph
OHC CH2
2k
Ph
C, Ar, 12 h
1b
5bk
, 40%
9
Ph
Ph
Additive (2 equiv)
TBHP (3 equiv)
10
11
12
13
14
15
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58
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60
+
(7)
PhCl, 100 o
C, Ar, 12 h
OHC
2a
1a
3aa
, trace
Additive = TEMPO, hydroquinone, 2,6-di-tert-butyl-4-methylphenol (BHT)
H(D)
0.36 D
Ph
Ph
D
2O (0.1 mL)
+
(8)
(9)
TBHP (3 equiv)
PhCl, 100 o
OHC
2a
C, Ar, 12 h
1a
3aa
, 71%
H(D)
only H
Ph
Ph
TBHP (3 equiv)
CD3CN, 100 o
+
C, Ar, 12 h
OHC
2a
1a
3aa
, 62%
The mechanism for this [3+2] annulation reaction was proposed (Scheme 4).4-6 In the presence of
peroxide, aldehyde 2a is easily transformed into the carbonyl radical A under heating conditions,5,6
which sequentially undergoes decarbonylation to afford the alkyl radical intermediate B.
Intermolecular addition of the intermediate B across the C≡C bond of the alkyne 1a selectively
generates the vinyl radical intermediate C, followed by rapidly annulation with the C=C bond in
the aldehyde 2a gives the new alkyl radical intermediate D. Finally, protonation of the intermediate
D assembles the desired product 3aa.
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Scheme 4. Possible Mechanism.
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+
t-BuOOH
t-BuO
OH
+
t-BuO
OH
H
O
O
CO
t-BuOH + H
2O, t-BuOH,
2O
B
2a
A
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Ph
1a
H
2a
t-BuOOH or/and
Ph
Ph
Ph
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and/or
2t-BuOO
3aa
C
D
Conclusions
In summary, we have developed a novel oxidative decarbonylative [3+2] annulation of terminal
alkynes with tertiary alkyl aldehyde for the synthesis of polysubstituted cyclopentenes and indenes.
This reaction enables the formation of two new C-C bonds using a metal-free oxidative
decarbonylation strategy, and represents a new oxidative radical-mediated intermolecular [3+2]
annulation of alkynes with alkyl radicals that are formed from decarbonylation of tertiary alkyl
aldehydes having an aldehyde group connected to the tertiary sp3-hybridized carbon atom.
Importantly, selectivity toward cyclopentenes and indenes is controllable and relies on the nature
of substrates, which makes this type of transformation useful in synthetic and medicinal chemistry.
Experimental Section
General Considerations:
The 1H and 13C NMR spectra were recorded in CDCl3 solvent on a NMR spectrometer using TMS as
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internal standard. HRMS was measured on an electrospray ionization (ESI) apparatus using time-of-
flight (TOF) mass spectrometry. Melting points are uncorrected.
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Typical Experimental Procedure for the Synthesis of Tertiary Alkyl Aldehydes (2):8
To a solution of aldehyde (10 mmol) in CH2Cl2 (50 mL) was added in one portion KOtBu (13 mmol),
followed immediately by allylbromide (20 mmol). The resulting mixture was stirred for 2h at room
temperature, and then water (20 mL) was added. The organic layer was further washed with water (3×10
mL), dried over MgSO4, filtered, and concentrated in vacuum. The resulting residue was purified by
flash column chromatography using petroleum ether/Et2O (9:1) eluent to give the title compound 2.
Typical Experimental Procedure for Decarbonylative Annulation of Terminal Alkynes with
Tertiary Alkyl Aldehydes Toward Cyclopentenes:
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To a Schlenk tube were added alkyne 1 (0.2 mmol), aldehyde 2 (2 equiv), TBHP (5 M in decane; 3
o
equiv), and PhCl (2 mL). Then the tube was charged with argon, and was stirred at 100 C (oil bath
temperature) under argon atmosphere for the indicated time until complete consumption of starting
material as monitored by TLC and/or GC-MS analysis. After the reaction was finished, the reaction
mixture was cooled to room temperature, diluted in diethyl ether, and washed with brine. The aqueous
phase was re-extracted with EtOAc (3×10 mL). The combined organic extracts were dried over MgSO4
and concentrated in vacuum. The resulting residue was purified by silica gel flash column
chromatography (hexane/ethyl acetate = 50:1) to afford the desired product 3.
(3,3,5-Trimethylcyclopent-1-en-1-yl)benzene (3aa): 27.5 mg, 74%; Colorless oil; 1H NMR (400 MHz,
CDCl3) δ: 7.37 (d, J = 7.6 Hz, 2H), 7.30 (t, J = 7.2 Hz, 2H), 7.20 (t, J = 7.2 Hz, 1H), 5.79 (s, 1H), 3.31
(dd, J = 13.2, 6.8 Hz, 1H), 2.12 (dd, J = 11.2, 10.0 Hz, 1H), 1.47 (dd, J = 12.8, 4.8 Hz, 1H), 1.18 (s,
3H), 1.12 (d, J = 6.8 Hz, 3H), 1.09 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 144.8, 137.4, 136.9, 128.4
(2C), 126.8, 126.5 (2C), 48.2, 44.3, 39.4, 30.3, 29.4, 21.4; LRMS (EI, 70 eV) m/z (%): 186 (M+, 19),
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171 (100), 91 (17); HRMS m/z (ESI) calcd for C14H19 ([M+H]+) 187.1481, found 187.1488.
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1-Methyl-4-(3,3,5-trimethylcyclopent-1-en-1-yl)benzene (3ba): 32.4 mg, 81%; Colorless oil; H
NMR (400 MHz, CDCl3) δ: 7.27 (d, J = 8.0 Hz, 2H), 7.12 (d, J = 7.2 Hz, 2H), 5.74 (s, 1H), 3.29 (dd, J
= 12.8, 6.4 Hz, 1H), 2.33 (s, 3H), 2.14-2.08 (m, 1H), 1.47 (dd, J = 12.4, 4.0 Hz, 1H), 1.17 (s, 3H), 1.12
(d, J = 7.2 Hz, 3H), 1.09 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 144.6, 136.5, 136.5, 134.0, 129.1
(2C), 126.4 (2C), 48.2, 44.2, 39.4, 30.4, 29.5, 21.4, 21.3; LRMS (EI, 70 eV) m/z (%): 200 (M+, 21), 185
(100), 143 (19); HRMS m/z (ESI) calcd for C15H21 ([M+H]+) 201.1638, found 201.1642.
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5-(4-Methoxyphenyl)-1,2-diphenylpentane-1,5-dione (3ca): 29.4 mg, 68%; Colorless oil; H NMR
(500 MHz, CDCl3) δ: 7.30 (d, J = 8.4 Hz, 2H), 6.85 (d, J = 8.4 Hz, 2H), 5.68 (s, 1H), 3.80 (s, 3H), 3.26
(d, J = 5.6 Hz, 1H), 2.10 (dd, J = 12.4, 8.8 Hz, 1H), 1.47 (dd, J = 12.8, 4.4 Hz, 1H), 1.17 (s, 3H), 1.11
(d, J = 6.7 Hz, 3H), 1.09 (s, 3H); 13C NMR (125 MHz, CDCl3) δ: 158.5, 144.1, 135.4, 129.4, 127.5
(2C), 113.7 (2C), 55.3, 48.1, 44.1, 39.4, 30.3, 29.5, 21.4; LRMS (EI, 70 eV) m/z (%): 216 (M+, 18), 201
(100), 172 (10); HRMS m/z (ESI) calcd for C15H21O ([M+H]+) 217.1587, found 217.1592.
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1-Bromo-4-(3,3,5-trimethylcyclopent-1-en-1-yl)benzene (3da): 31.7 mg, 60%; Yellow oil; H NMR
(400 MHz, CDCl3) δ: 7.42 (d, J = 8.0 Hz, 2H), 7.23 (d, J = 8.0 Hz, 2H), 5.79 (s, 1H), 3.26 (dd, J = 12.4,
6.0 Hz, 1H), 2.15-2.09 (m, 1H), 1.47 (dd, J = 12.8, 4.8 Hz, 1H), 1.18 (s, 3H), 1.09 (d, J = 2.4 Hz, 6H);
13C NMR (100 MHz, CDCl3) δ: 143.8, 138.2, 135.8, 131.4 (2C), 128.1 (2C), 120.5, 48.1, 44.4, 39.3,
30.2, 29.3, 21.2; LRMS (EI, 70 eV) m/z (%): 266 (M++2, 16), 264 (M+, 16), 251 (82), 170 (100); HRMS
m/z (ESI) calcd for C14H18Br ([M+H]+) 265.0586, found 265.0588.
1-Chloro-4-(3,3,5-trimethylcyclopent-1-en-1-yl)benzene (3ea): 31.7 mg, 72%; d Yellow oil; 1H NMR
(400 MHz, CDCl3) δ: 7.27 (d, J = 5.6 Hz, 4H), 5.77 (s, 1H), 3.26 (dd, J = 12.8, 6.4 Hz, 1H), 2.14-2.09
(m, 1H), 1.47 (dd, J = 12.8, 3.2 Hz, 1H), 1.17 (s, 3H), 1.09 (s, 6H); 13C NMR (100 MHz, CDCl3) δ:
143.8, 138.0, 135.3, 132.4, 128.5 (2C), 127.8 (2C), 48.2, 44.4, 39.4, 30.2, 29.4, 21.2; LRMS (EI, 70 eV)
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m/z (%): 222 (M++2, 17), 220 (M+, 52), 176 (21), 105 (100); HRMS m/z (ESI) calcd for C14H18Cl
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([M+H]+) 221.1092, found 221.1095.
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1-Chloro-3-(3,3,5-trimethylcyclopent-1-en-1-yl)benzene (3fa): 30.8 mg, 70%; Colorless oil; 1H NMR
(400 MHz, CDCl3) δ: 7.34 (s, 1H), 7.23 (d, J = 4.4 Hz, 1H), 7.18 (dd, J = 6.0, 3.2 Hz, 1H), 5.81 (s, 1H),
3.31-3.22 (m, 1H), 2.12 (dd, J = 12.8, 8.4 Hz, 1H), 1.47 (dd, J = 12.8, 5.2 Hz, 1H), 1.18 (s, 3H), 1.10 (d,
J = 7.6 Hz, 6H); 13C NMR (100 MHz, CDCl3) δ: 143.6, 138.7, 134.1, 129.4, 126.6, 126.5, 124.5, 48.0,
44.2, 39.3, 30.0, 29.2, 21.1; LRMS (EI, 70 eV) m/z (%): 222 (M++2, 7), 220 (M+, 23), 205 (100); HRMS
m/z (ESI) calcd for C14H18Cl ([M+H]+) 221.1092, found 221.1095.
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1-Chloro-2-(3,3,5-trimethylcyclopent-1-en-1-yl)benzene (3ga): 34.3 mg, 78%; Colorless oil; 1H NMR
(400 MHz, CDCl3) δ: 7.34 (d, J = 7.2 Hz, 1H), 7.18-7.13 (m, 3H), 5.60 (s, 1H), 3.48-3.40 (m, 1H), 2.08
(dd, J = 12.4, 8.0 Hz, 1H), 1.39 (dd, J = 12.4, 7.6 Hz, 1H), 1.19 (s, 3H), 1.11 (s, 3H), 0.92 (d, J = 6.8
Hz, 3H)); 13C NMR (100 MHz, CDCl3) δ: 144.0, 141.1, 137.1, 132.5, 130.7, 129.6, 127.8, 126.2, 48.6,
44.3, 41.0, 29.7, 28.1, 20.0; LRMS (EI, 70 eV) m/z (%): 222 (M++2, 7), 220 (M+, 21), 205 (100); HRMS
m/z (ESI) calcd for C14H18Cl ([M+H]+) 221.1092, found 221.1095.
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2,4-Dimethoxy-1-(3,3,5-trimethylcyclopent-1-en-1-yl)benzene (3ha): 32.5 mg, 66%; Yellow oil; H
NMR (400 MHz, CDCl3) δ: 7.13 (d, J = 8.8 Hz, 1H), 6.44 (d, J = 6.8 Hz, 2H), 5.72 (s, 1H), 3.80 (s, 6H),
3.43 -3.34 (m, 1H), 2.03 (dd, J = 12.4, 8.0 Hz, 1H), 1.36 (dd, J = 12.4, 6.8 Hz, 1H), 1.17 (s, 3H), 1.08 (s,
3H), 0.97 (d, J = 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 159.6, 158.2, 142.7, 138.4, 130.1, 119.4,
104.0, 98.8, 55.3, 48.2, 43.9, 40.5, 30.1, 28.9, 20.8; LRMS (EI, 70 eV) m/z (%): 246 (M+, 24), 231
(100), 93 (11); HRMS m/z (ESI) calcd for C16H23O2 ([M+H]+) 247.1693, found 247.1699.
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9,9-Dimethyl-7,7a,8,9-tetrahydrocyclopenta[a]phenalene (3ia): 21.5 mg, 46%; Colorless oil; H
NMR (400 MHz, CDCl3) δ: 7.73-7.65 (m, 3H), 7.43 (t, J = 7.6 Hz, 1H), 7.37 (t, J = 7.6 Hz, 1H), 7.23 (s,
1H), 6.10 (s, 1H), 3.34 (dd, J = 14.8, 5.6 Hz, 1H), 3.28-3.22 (m, 1H), 2.81 (t, J = 13.6 Hz, 1H), 2.22 (dd,
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J = 12.4, 7.2 Hz, 1H), 1.57-1.52 (m, 2H), 1.26 (s, 3H), 1.16 (s, 3H); 13C NMR (100 MHz, CDCl3) δ:
139.4, 135.9, 133.7, 133.3, 130.6, 129.2, 127.3, 126.0, 125.6, 125.5, 124.3, 120.9, 47.5, 44.9, 41.8, 39.1,
29.9, 28.0; LRMS (EI, 70 eV) m/z (%): 234 (M+, 28), 219 (100), 101 (10); HRMS m/z (ESI) calcd for
C18H19 ([M+H]+) 235.1481, found 235.1484.
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3-(3,3,5-Trimethylcyclopent-1-en-1-yl)pyridine (3ja): 26.9 mg, 72%; Yellow oil; 1H NMR (400 MHz,
CDCl3) δ: 8.63 (s, 1H), 8.44 (s, 1H), 7.63 (d, J = 8.0 Hz, 1H), 7.27-7.21 (m, 1H), 5.87 (s, 1H), 3.31 (dd,
J = 13.6, 6.8 Hz, 1H), 2.14 (dd, J = 12.8, 8.4 Hz, 1H), 1.51-1.48 (m, 1H), 1.19 (s, 3H), 1.11 (s, 6H); 13C
NMR (100 MHz, CDCl3) δ: 147.7, 147.6, 141.6, 139.1, 133.4, 132.3, 123.1,47.9, 44.3, 39.1, 29.9, 29.0,
20.8; LRMS (EI, 70 eV) m/z (%):187 (M+, 18), 172 (100), 144 (11); HRMS m/z (ESI) calcd for C13H18N
([M+H]+) 188.1434, found 188.1439.
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3-(3,3,5-trimethylcyclopent-1-en-1-yl)thiophene (3ka): 25.0 mg, 65%; Yellow oil; H NMR (400
MHz, CDCl3) δ: 7.24 (t, J = 4.0 Hz, 1H), 7.18 (d, J = 4.8 Hz, 1H), 7.09 (s, 1H), 5.73 (s, 1H), 3.21-3.13
(m, 1H), 2.09 (dd, J = 12.8, 8.8 Hz, 1H), 1.47 (dd, J = 12.8, 4.4 Hz, 1H), 1.20 (d, J = 7.2 Hz, 3H), 1.18
(s, 3H), 1.09 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 139.8, 138.2, 136.3, 126.5, 125.1, 119.8, 48.0,
44.1, 40.2, 30.2, 29.6, 21.7; LRMS (EI, 70 eV) m/z (%):192 (M+, 26), 177 (100), 143 (36); HRMS m/z
(ESI) calcd for C12H17S ([M+H]+) 193.1045, found 193.1047.
1-(3,3,5-Trimethylcyclopent-1-en-1-yl)cyclohex-1-ene (3la): 21.7 mg, 57%; Colorless oil; 1H NMR
(400 MHz, CDCl3) δ: 5.71 (s, 1H), 5.36 (s, 1H), 3.01-2.96 (m, 1H), 2.27-2.21 (m, 1H), 2.14-2.06 (m，
3H), 1.98 (dd, J = 12.8, 9.2 Hz, 1H), 1.70 -1.64 (m, 2H), 1.62-1.55 (m, 2H), 1.40 (dd, J = 12.8, 2.8 Hz,
1H), 1.14 (d, J = 7.2 Hz, 3H), 1.12 (s, 3H), 1.04 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 146.2, 133.9,
132.5, 124.5, 47.7, 43.9, 38.7, 30.4, 30.3, 26.5, 25.7, 22.9, 22.5, 22.4; LRMS (EI, 70 eV) m/z (%): 190
(M+, 30), 175 (100), 133 (20); HRMS m/z (ESI) calcd for C14H23 ([M+H]+) 191.1794, found 191.1798.
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((3,3,5-Trimethylcyclopent-1-en-1-yl)ethynyl)benzene (3ma): 17.2 mg, 41%; Yellow oil; H NMR
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(400 MHz, CDCl3) δ: 7.45 -7.43 (m, 2H), 7.30 (d, J = 5.6 Hz, 3H), 5.92 (s, 1H), 2.04-1.98 (m, 1H), 2.01
(dd, J = 12.4, 4.0 Hz, 1H), 1.35-1.30 (dd, J = 12.8, 7.6 Hz, 1H), 1.21 (d, J = 6.8 Hz, 3H), 1.14 (s, 3H),
1.07 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 147.4, 131.5 (2C), 128.2 (2C), 127.9, 127.3, 123.6, 91.2,
86.1, 47.9, 44.9, 42.1, 29.5, 27.8, 20.2; LRMS (EI, 70 eV) m/z (%): 210 (M+, 45), 195 (100), 151 (13);
HRMS m/z (ESI) calcd for C16H19 ([M+H]+) 211.1481, found 211.1487.
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Phenyl(3,3,5-trimethylcyclopent-1-en-1-yl)methanone (3oa): 19.7 mg, 46%; Yellow oil; H NMR
(400 MHz, CDCl
1H), 3.38-3.30 (m, 1H), 2.10 (dd, J = 12.8, 8.0 Hz, 1H), 1.44 (dd, J = 12.8, 7.2 Hz, 1H), 1.25 (s, 3H),
1.20 (d, J = 6.8 Hz, 3H), 1.06 (s, 3H); 13C NMR (100 MHz, CDCl
) δ: 195.0, 154.8, 145.2, 139.1, 132.0,
129.0 (2C), 128.2 (2C), 47.4, 45.4, 39.2, 29.2, 27.6, 20.1; LRMS (EI, 70 eV) m/z (%): 214 (M+, 26), 105
(100), 77 (42) ; HRMS m/z (ESI) calcd for C15
19O ([M+H]+) 215.1430, found 215.1427.
3
) δ: 7.76 (d, J = 7.2 Hz, 2H), 7.53 (t, J = 7.2 Hz, 1H), 7.44 (t, J = 7.6 Hz, 2H), 6.17 (s,
3
H
1
N,3,3,5-tetramethyl-N-phenylcyclopent-1-ene-1-carboxamide (3pa): 22.8 mg, 47%; Yellow oil; H
NMR (400 MHz, CDCl3) δ: 7.33 (t, J = 7.6 Hz, 2H), 7.27 (s, 1H), 7.15 (d, J = 7.6 Hz, 2H), 5.43 (s, 1H),
3.35 (s, 3H), 2.56-2.51 (m, 1H), 1.74 (dd, J = 12.4, 7.6 Hz, 1H), 1.12 (dd, J = 12.0, 8.0 Hz, 1H), 1.04 (d,
J = 6.8 Hz, 3H), 0.90 (s, 3H), 0.80 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 168.8, 145.9, 144.4, 141.0,
129.0 (2C), 127.1 (2C), 126.9, 47.6, 44.5, 39.9, 37.4, 28.7, 26.7, 19.7; LRMS (EI, 70 eV) m/z (%): 243
(M+, 19), 137 (100), 77 (13); HRMS m/z (ESI) calcd for C16H22NO ([M+H]+) 244.1696, found
244.1701.
2,2,5-Trimethyl-2,5,10,10a-tetrahydrobenzo[b]cyclopenta[e]azepin-4(1H)-one (4pa): 10.1 mg, 21%;
Yellow oil; 1H NMR (400 MHz, CDCl3) δ: 7.27-7.24 (m, 1H), 7.11 (t, J = 4.2 Hz, 3H), 5.65 (d, J = 1.6
Hz, 1H), 3.71 (dd, J = 15.2, 7.2 Hz, 1H), 3.37 (s, 3H), 3.21 (dd, J = 13.6, 6.4 Hz, 1H), 2.39 (d, J = 13.6
Hz, 1H), 1.79 (dd, J = 12.0, 7.2 Hz, 1H), 1.36 (t, J = 13.2 Hz, 1H), 1.03 (s, 3H), 0.81 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ: 169.2, 143.7, 142.7, 138.8, 133.4, 130.7, 127.3, 125.3, 122.4, 49.9, 44.6, 44.1,
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35.3, 34.3, 28.8, 26.0; LRMS (EI, 70 eV) m/z (%): 241 (M+, 100), 199 (23), 132 (12); HRMS m/z (ESI)
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calcd for C16H20NO ([M+H]+) 242.1539, found 242.1542.
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(3,3-Diethyl-5-methylcyclopent-1-en-1-yl)benzene (3ab): 24.8 mg, 58%; Colorless oil; 1H NMR (400
MHz, CDCl3) δ: 7.36 (d, J = 8.0 Hz, 2H), 7.30 (t, J = 7.6 Hz, 2H), 7.20 (t, J = 7.2 Hz, 1H), 5.73 (s, 1H),
3.31-3.22 (m, 1H), 2.08 (dd, J = 13.2, 8.8 Hz, 1H), 1.51-1.37 (m, 5H), 1.09 (d, J = 6.8 Hz, 3H), 0.88 (t, J
= 7.6 Hz, 3H), 0.82 (t, J = 7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 146.1, 137.0, 134.6, 128.2 (2C),
126.6, 126.4 (2C), 51.6, 42.7, 39.2, 32.3, 31.8, 21.2, 9.3, 9.0; LRMS (EI, 70 eV) m/z (%): 214 (M+, 4),
185 (100), 143 (14); HRMS m/z (ESI) calcd for C16H23 ([M+H]+) 215.1794, found 215.1799.
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(3-Ethyl-3,5-dimethylcyclopent-1-en-1-yl)benzene (3ac): 26.0 mg, 65%; d.r. = 1:1; Colorless oil; H
NMR (400 MHz, CDCl3) δ: 7.37 (t, J = 7.2 Hz, 2.1H), 7.30 (t, J = 7.6 Hz, 2.1H), 7.20 (t, J = 7.2 Hz,
1.0H), 5.77 (s, 1H), 3.35-3.24 (m, 1.0H), 2.19 (dd, J = 12.8, 8.8 Hz, 0.5H), 2.01 (dd, J = 12.8, 8.4 Hz,
0.5H), 1.54-1.33 (m, 3.5H), 1.13 (d, J = 6.0 Hz, 2.1H), 1.10 (d, J = 7.2 Hz, 2.1H), 1.05 (s, 1.5H), 0.91 (t,
J = 7.6 Hz, 1.6H), 0.85 (t, J = 7.6 Hz, 1.6H); 13C NMR (100 MHz, CDCl3) δ: 145.4, 145.2, 137.0, 136.8,
136.3, 135.7, 128.2 (3C), 126.6, 126.4 (2C), 47.9, 47.8, 45.5, 39.4, 38.7, 34.9, 34.8, 27.8, 26.3, 21.5,
20.9, 9.6, 9.4; LRMS (EI, 70 eV) m/z (%): 200 (M+, 6), 171 (100), 143 (22); HRMS m/z (ESI) calcd for
C15H21 ([M+H]+) 201.1638, found 201.1642.
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(3,3,5-Triethylcyclopent-1-en-1-yl)benzene (3ad): 23.3 mg, 51%; Colorless oil; H NMR (400 MHz,
CDCl3) δ: 7.35-7.30 (m, 4H), 7.20 (t, J = 6.8 Hz, 1H), 5.71 (s, 1H), 3.11 (d, J = 8.0 Hz, 1H), 1.98 (dd, J
= 13.2, 8.8 Hz, 1H), 1.74-1.72 (m, 1H), 1.52-1.35 (m, 5H), 1.19-1.09 (m, 1H), 0.90-0.80 (m, 9H); 13C
NMR (100 MHz, CDCl3) δ: 145.3, 137.4, 135.2, 128.1 (2C), 126.6, 126.4 (2C), 51.5, 46.4, 39.4, 32.3,
31.9, 27.5, 11.8, 9.3, 9.0; LRMS (EI, 70 eV) m/z (%): 228 (M+, 4), 199 (100), 143 (14); HRMS m/z
(ESI) calcd for C17H25 ([M+H]+) 229.1951, found 229.1954.
3-(3,5-Dimethyl-3-phenylcyclopent-1-en-1-yl)pyridine (3je): 18.4 mg, 37%; d.r. = 1:1; Yellow oil; 1H
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NMR (400 MHz, CDCl3) δ: 8.70 (s, 1.0H), 8.49 (d, J = 4.0 Hz, 1.0H), 7.71 (d, J = 7.6 Hz, 1.0H), 7.39
(d, J = 8.0 Hz, 1.0H), 7.37-7.26 (m, 4.2H), 7.23-7.16 (m, 1.0H), 6.20 (s, 0.5H), 6.17 (s, 0.5H), 3.44-3.33
(m, 1.0H), 2.61 (dd, J = 13.2, 8.8 Hz, 0.5H), 2.49 (dd, J = 12.8, 8.0 Hz, 0.5H), 1.94 (dd, J = 12.8, 6.0
Hz, 0.5H), 1.85 (dd, J = 13.2, 5.2 Hz, 0.5H), 1.60 (s, 1.5H), 1.49 (s, 1.5H), 1.18 (d, J = 6.8 Hz, 1.5H),
1.05 (d, J = 6.8 Hz, 1.5H); 13C NMR (100 MHz, CDCl3) δ: 150.3, 149.8, 148.1, 148.0, 147.9, 146.5,
143.6, 136.8, 136.6, 133.7, 128.3, 128.3, 125.9, 125.8, 125.7, 123.2, 51.8, 51.5, 49.8, 49.8, 39.4, 39.0,
29.8, 28.5, 20.8, 19.9; LRMS (EI, 70 eV) m/z (%): 249 (M+, 16), 211 (M+, 27), 173 (100); HRMS m/z
(ESI) calcd for C18H20N ([M+H]+) 250.1590, found 250.1597.
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3-(1,1-Dimethyl-1H-inden-3-yl)pyridine (3jh): 23.0 mg, 52%; Yellow oil; H NMR (400 MHz,
CDCl3) δ: 8.85 (s, 1H), 8.60 (d, J = 4.4 Hz, 1H), 7.89 (d, J = 7.6 Hz, 1H), 7.45-7.37 (m, 3H), 7.30-7.28
(m, 2H), 6.49 (s, 1H), 1.41 (s, 6H); 13C NMR (100 MHz, CDCl3) δ: 13C NMR (101 MHz, CDCl3) δ
154.2, 148.8, 148.7, 145.4, 141.0, 137.7, 134.8, 131.6, 126.5, 125.8, 123.4, 121.7, 120.2, 48.8, 24.6.;
LRMS (EI, 70 eV) m/z (%): 221 (M+, 13), 177 (15), 143 (100); HRMS m/z (ESI) calcd for C16H16N
([M+H]+) 222.1277, found 222.1281.
N,1,1-trimethyl-N-phenyl-1H-indene-3-carboxamide (3ph): 28.3 mg, 51%; d.r. = 2:1; Yellow oil; 1H
NMR (400 MHz, CDCl3) δ: 7.42 (t, J = 7.6 Hz, 3.0H), 7.32-7.17 (m, 4.5H), 7.09 (t, J = 7.6 Hz, 0.3H),
7.00 (t, J = 7.6 Hz, 0.7H), 6.75-6.69 (m, 1.0H), 6.58 (t, J = 7.6 Hz, 0.3H), 6.21 (d, J = 7.6 Hz, 0.3H),
3.23 (s, 1.0H), 3.13 (s, 2.0H), 1.79 (s, 4.0H), 1.65 (s, 2.1H); 13C NMR (100 MHz, CDCl3) δ: 13C NMR
(101 MHz, CDCl3) δ 164.9, 164.8, 150.9, 150.8, 149.9, 149.8, 147.7, 142.5, 128.8, 128.7, 128.7, 128.0,
127.4, 127.1, 126.3, 126.0 (2C), 125.9, 125.8, 123.8, 121.6, 120.5, 119.8, 118.7, 107.7, 107.6, 41.3,
41.2, 30.5, 29.2, 26.1, 25.8.; LRMS (EI, 70 eV) m/z (%): 277 (M+, 27), 219 (100), 175 (18); HRMS m/z
(ESI) calcd for C19H20NO ([M+H]+) 278.1539, found 278.1543.
(3,3-Dimethylbut-1-en-1-yl)benzene (5aj): 22.4 mg, 70%; d.r. = 1.25:1; Colorless liquid; 1H NMR
(400 MHz, CDCl3) δ: 7.37-7.35 (m, 1.0H), 7.31-7.23 (m, 2.1H), 7.22-7.17 (m, 2.1H), 6.41 (d, J = 12.8
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Hz, 0.5H), 6.29 (s, 0.5H), 6.27 (s, 0.4H), 5.60 (d, J = 12.4 Hz, 0.5H), 1.12 (s, 4.2H), 0.98 (s, 5H); 13C
NMR (100 MHz, CDCl3) δ: 142.6, 141.8, 139.4, 138.0, 128.9, 128.5, 127.5, 127.1, 126.7, 126.1, 126.0,
124.5 (2C), 34.2, 33.3, 31.2, 29.6; LRMS (EI, 70 eV) m/z (%): 160 (M+, 30), 145 (100), 117 (31);
HRMS m/z (ESI) calcd for C12H17 ([M+H]+) 161.1325, found 161.1331.
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1-Methyl-4-(3-phenylprop-1-en-1-yl)benzene (5bk): 16.6 mg, 40%; d.r. = 2:1; Colorless liquid; 1H
NMR (400 MHz, CDCl3) δ: 7.32-7.09 (m, 9.7H), 6.56 (d, J = 11.2 Hz, 0.6H), 6.43 (d, J = 16.0 Hz,
0.3H), 6.34-6.28 (m, 0.3H), 5.85-5.78 (m, 0.6H), 3.69 (d, J = 7.6 Hz, 1.3H), 3.54 (d, J = 6.4 Hz, 0.6H),
2.35 (s, 2.0H), 2.32 (s, 0.9H); 13C NMR (100 MHz, CDCl3) δ: 141.8, 140.9, 136.5, 134.4, 130.9, 130.0,
129.8, 129.2, 128.9, 128.6, 128.6, 128.5, 128.4 (2C), 128.3, 128.2, 126.1, 126.0, 125.9, 39.3, 37.9, 34.7,
21.2; LRMS (EI, 70 eV) m/z (%): 208 (M+, 91), 193 (92), 178 (38), 115 (100); HRMS m/z (ESI) calcd
for C16H17 ([M+H]+) 209.1325, found 209.1332.
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Supporting Information Available: Copies of H and C spectra. This material is available free of
charge via the Internet at http://pubs.acs.org.
Acknowledgments. We thank the Natural Science Foundation of China (Nos. 21472039 and
21625203) and the Jiangxi Province Science and Technology Project (Nos. 20165BCB18007 and
20171ACB20015) for financial support.
References and notes
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Natural Aminocyclopentitol Glycosidase Inhibitors:ꢀ Mannostatins, Trehazolin, Allosamidins,
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Paraherquamides, Brevianamides, and Asperparalines:ꢀ Laboratory Synthesis and Biosynthesis.
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Soc. Rev. 2009, 38, 3102-3116. Via other organocatalysed [3+2] annulation, see: (e) Jin, Z.;
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(4) For papers on the synthesis of cyclopentenes via radical-mediated [3+2] annulation of 2-
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Cations in Cascade Reactions: From Carbocycles to Heterocycles. Acc. Chem. Res. 2016, 49,
1957-1968. Via radical-mediated [3+2] annulation with alkenes for the synthesis of
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Cyclopentane Synthesis via Free-Radical-Mediated Addition of Functionalized Alkenes to
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Cascade Radical Addition–Cyclization Halogen Atom Transfer between Alkynes and
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Silver-Catalyzed Intermolecular [3+2]/[5+2] Annulation of N-Arylpropiolamides with Vinyl
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1070-1082. (d) Chen, Z.-M.; Zhang, X.-M.; Tu, Y.-Q. Radical Aryl Migration Reactions and
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Synthetic Applications. Chem. Soc. Rev. 2015, 44, 5220-5245. (e) Song, R.-J. Liu, Y.; Xie, Y.-X.;
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Aliphatic Aldehydes with Azaarenes: Successful Minisci-Type Alkylation of Various
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