Difunctional additions to 1-cyclopropylallenes: an efficient and stereospecific method for the synthesis of 2,6-difunctional-1,3-hexadienes

Article abstract of DOI:10.1016/j.tetlet.2009.02.055

The difunctional additions of electrophiles and nucleophiles to 1-cyclopropylallenes were investigated. Two different functional groups were introduced at the same time to give 2,6-difunctional-1,3-hexadienes stereoselectively in good yields.

Full text of DOI:10.1016/j.tetlet.2009.02.055

Tetrahedron Letters 50 (2009) 1947–1950
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Difunctional additions to 1-cyclopropylallenes: an efficient and
stereospecific method for the synthesis of 2,6-difunctional-1,3-hexadienes
Bo Meng a, Lei Yu b, Xian Huang a,c,
*
a Department of Chemistry, Zhejiang University (Xixi Campus), Hangzhou 310028, People’s Republic of China
b School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, People’s Republic of China
c State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
The difunctional additions of electrophiles and nucleophiles to 1-cyclopropylallenes were investigated.
Two different functional groups were introduced at the same time to give 2,6-difunctional-1,3-hexadi-
enes stereoselectively in good yields.
Received 23 November 2008
Revised 4 February 2009
Accepted 6 February 2009
Available online 13 February 2009
Ó 2009 Elsevier Ltd. All rights reserved.
1-Cyclopropylallenes 1, which contain both a cyclopropyl group
and an allene structural unit, are a kind of useful building blocks in
organic synthesis.1 The special molecule structure of 1-cyclo-
propylallenes makes them act like allenes2 and sometimes methyl-
enecyclopropanes3 in organic reactions. Recently, we have
investigated the electrophilic additions of 1-cyclopropylallenes.4
In these reactions, the electrophilic group was first added to the
center carbon of allene group of 1-cyclopropylallenes to give the
intermediate carbon cation 2. The following b-scission of 2 gave
the homoallylic carbon cation 3, which could be transformed to
the corresponding homoallylic derivatives (Scheme 1). It is notable
that, in these reactions, the stereoselectivities are generally good
and one even two multisubstituted C@C double bonds could be
generated stereoselectively in the final product. Hence, this would
give an efficient and stereospecific method for the synthesis of
multisubstituted olefins.
introduced simultaneously by one molecule of electrophile and an-
other molecule of nucleophile, which would provide an efficient
and stereoselective tool for the synthesis of 2,6-difunctional-1,3-
hexadienes.
We initially examined the difunctional reaction of 1-cyclo-
propylallene 1a with NIS–MBr system. When 1a, NIS and KBr were
stirred in DCM at room temperature for 15 h, the desired difunc-
tional adduct 4a could be obtained in 43% yield (Table 1, entry
1). Further screening demonstrated that employing THF as solvent
would enhance the yield of 4a (Table 1, entry 4) and NaBr should
be a better bromo source (Table 1, entry 7).
With the optimized reaction conditions in hand, we next exam-
ined the application scope of this reaction. The experimental re-
sults were listed in Table 2. It is obvious that Cl, Br, or I group
could be conveniently introduced to the 2- or 6-position of the
product as wish (Table 2, entries 1–6). The yields of 4 were gener-
Being able to introduce two different functional groups at the
same time, difunctional reactions are important in organic synthe-
sis.5 On the basis of our previous investigations on electrophilic
additions of 1-cyclopropylallenes, here, we wish to report our re-
cent investigation results on difunctional reactions of 1-cyclo-
propylallenes. Specially, two changeable functional groups were
Table 1
The reaction of 1a with NIS–MBr systema
I
solvent
+ NIS + MBr
C
Br
N , temp
2
Ph
Ph
Yield of 4ac (%)
1a
4a
H C
2
Entry
MBr
Solvent
Timeb (h)
2
+
R
E
-scission
2
R
C
C
1
2
3
4
5
6
7
KBr
KBr
KBr
KBr
DCM
DMF
MeCN
THF
THF
THF
15
6
8
15
10
3
43
27
48
52
31
59
77
1
C
E
1
2
R
E
R
R
1
R
1
2
3
Bu4NBr
LiBr
NaBr
Scheme 1. Electrophilic addition of 1-cyclopropylallenes to generate homoallylic
THF
0.5
derivatives.
a
0.3 mmol of 1a, NIS and MBr, and 2 mL of solvent were employed.
The reaction was monitored by TLC (eluent: petroleum ether).
Isolated yields.
b
c
* Corresponding author. Tel.: +86 571 88807077; fax: +86 571 88807077.
E-mail address: huangx@mail.hz.zj.cn (X. Huang).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.02.055

1948
B. Meng et al. / Tetrahedron Letters 50 (2009) 1947–1950
Table 2
Br
Br
Dihalogenation of 1-cyclopropylallenes (1)a
X
I
I
THF
N , r.t.
+ NXS + MY
C
Y
2
H
H
R
Br
Br
R
NOE
H
H
CH3
4
1
NOE
Yield of 4b (%)
H3C
Entry
R
X
MY
1Z, 3Z-4k
1
2
3
4
5
6
7
8
9
Ph (1a)
1a
1a
1a
1a
1a
p-CH3C6H4 (1b)
p-ClC6H4 (1c)
Bn (1d)
I
I
I
Br
Br
Cl
I
I
I
NaBr
NaCl
NaI
NaCl
NaBr
NaCl
NaBr
NaBr
NaBr
77 (4a)
61 (4b)
87 (4c)
67 (4d)
74 (4e)
69 (4f)
85 (4g)
Br
Br
H
H
H
H
NOE
NOE
I
I
79 (4h)
54 (4i) (Z/E = 81:19)c
Cl
Br
H
H
a
NOE
0.3 mmol of 1, NIS and MY, and 2 mL of THF were employed.
Isolated yields.
NOE
b
c
The ratio of isomers was calculated from 1H NMR spectrum.
Cl
1Z, 3Z-4m
1Z, 3Z-4o
ally good and only Z-isomers were obtained except in entry 9,
when R was Bn, which had a lower steric hindrance. The configu-
rations of 4c and 4h were determined by the NOESY spectrum
study (Fig. 1).
When distally substituted 1-cyclopropylallenes were employed,
two multisubstituted C@C double bonds could be generated in the
product to give the 1Z, 3Z isomer as the major product (Table 3).
The configurations of 4k, 4m, and 4o were established on the
NOESY spectrum studies (Fig. 2).
Figure 2. Configurations of 1Z, 3Z-4k, 4m, 4o.
other nucleophiles were employed. These include alcohol, carbox-
ylic acid, amide, and NaNCS (Table 4, entries 1–5). Similarly, PhSe+,
generated by N-phenylselenophthalimide (NPSP), could also be
employed as electrophile to produce the corresponding 2,6-difunc-
tional adducts (Table 4, entries 6 and 7). It is notable that all these
reactions underwent with excellent stereoselectivity. The configu-
rations of 5b and 5g were established on the NOESY spectrum
studies (Fig. 3).
A possible mechanism of this reaction was shown in Scheme 2.
Electrophilic addition of electrophiles to 1 would give the interme-
diate allylic carbon cation 5, which could be 5(A) and 5(B) in reso-
nance.4 In 5(A), R2 was inclined to be at the same side with E due to
the steric hindrance factor while in 5(B), R1 was inclined to be at
the same side with the hydrogen atom. These determined the con-
figuration of the 1-position and 3-position C@C double bonds in
product 4.6 Further reaction of 5(B) with nucleophiles would give
the final product 4 in 1Z, 3Z configuration as the overwhelming
major product (Table 3). When R1 = alkyl group, the carbon cation
in 5(B) could not be well stabilized. Thus, the yield of 4 declined
(Table 2, entry 9). Meanwhile, when R1 or R2 were lower steric hin-
drance groups, the selectivity on the 3-position or 1-position C@C
double bonds declined, respectively (Table 2, entry 9 and Table 3,
entry 5).
Furthermore, the application scope of this reaction was not lim-
ited only to the synthesis of 2,6-dihalo-1,3-hexadienes. The corre-
sponding difunctional adducts could be smoothly obtained when
I
I
Br
I
H
H
NOE
H
NOE
H
Cl
Z-4c
Z-4h
Figure 1. Configurations of Z-4c, 4h.
Table 3
Dihalogenation of 1,3-disubstituted-1-cyclopropylallenesa
1
2
R
R
2
X
R
Y
Table 4
X
Difunctional additions of 1a with other electrophiles and nucleophiles
Y
1
R
E
A (1Z, 3Z)
C (1Z, 3E)
THF
1
solvent
N2, r.t.
C
+
NXS + NaY
X
R
+ E+ + Nu-
N , r.t.
2
1
2
C
R
R
Nu
Y
2
R
X
Y
Ph
Ph
1
1
2
R
R
1a
5
X = I, Br, Cl
Y = I, Br, Cl
B (1E, 3Z)
D (1E, 3E)
Entry
Electrophile
Nucleophile
Yield of 5e (%)
isomers of 4
1a
2a
3b
4b
5c
6d
7d
NIS
NIS
NIS
NIS
NBS
NPSP
NPSP
EtOH
82 (5a)
76 (5b)
87 (5c)
69 (5d)
21 (5e)
76 (5f)
65 (5g)
Entry
R1, R2
X
Y
Yield of 4 (%) (A/B/C/D)b
(CH3)2CHOH
NaOAc
NaNCS
PhCONH2
EtOH
1
2
3
4
5
6
7
C6H5, p-BrC6H4 (1e)
o-CH3C6H4, p-BrC6H4 (1f)
I
I
I
I
I
I
Br
Br
Br
Br
Br
Br
Cl
Cl
76 (86/14/0/0) (4j)
68 (89/11/0/0) (4k)
71 (85/15/0/0) (4l)
81(89/11/0/0) (4m)
58 (60/40/0/0) (4n)c
69(91/9/0/0) (4o)
61(66/34/0/0) (4p)
m-CH3C6H4, p-BrC6H4 (1g)
p-ClC6H4, p-BrC6H4 (1h)
C6H5, C2H5 (1i)
C6H5, p-BrC6H4 (1e)
C6H5, C6H5 (1j)
NaBr
a
0.3 mmol of 1a, NIS, and 2 mL of nucleophile were employed.
b
c
0.3 mmol of 1a, NIS, nucleophile, and 2 mL of THF were employed.
0.3 mmol of 1a, NBS, PhCONH2, and 2 ml of EtOAc were employed.
0.3 mmol of 1a, NPSP, nucleophile, and 2 mL of THF were employed.
Isolated yields.
a
0.3 mmol of 1, NXS and NaY, and 2 mL of THF were employed.
Isolated yields.
b
c
d
e
The ratio of isomers was calculated from 1H NMR spectrum.

B. Meng et al. / Tetrahedron Letters 50 (2009) 1947–1950
1949
Research Program of China (973 Program, 2009CB825300), and
CAS Academician Foundation of Zhejiang Province for financial
support.
I
PhSe
O
Br
H
H
NOE
NOE
Supplementary data
Z-5b
Z-5g
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2009.02.055.
Figure 3. Configurations of Z-5b, 5g.
References and notes
1. 1-Cyclopropylallenes could be conveniently prepared by the classical reaction
of cyclopropyl Grignard reagent with toluene-4-sulfonic acid prop-2-ynyl ester
catalyzed by copper (I) bromide. For details see: Brandsma, L.; Verkruijsse, H. D.
Synthesis of Acetylenes, Allenes and Cumlenes; Elsevier: Netherlands, 1981.
2. For recent reviews and accounts of allenes see: (a) Yamamoto, Y.;
Radhakrishnan, U. Chem. Soc. Rev. 1999, 28, 199; (b) Ma, S. Acc. Chem. Res.
2003, 36, 701; (c) Larock, R. C. J. Organomet. Chem. 1999, 576, 111; (d) Grigg, R.;
Sridharan, V. J. Organomet. Chem. 1999, 576, 65; (e) Zimmer, R.; Dinesh, C. U.;
Nandanan, E.; Khan, F. A. Chem. Rev. 2000, 100, 3067; (f) Hashmi, A. S. K. Angew.
Chem. 2000, 112, 3737; Hashmi, A. S. K. Angew. Chem., Int. Ed. 2000, 39, 3590;
(g) Ma, S.; Li, L. Synlett 2001, 1206; (h) Reissing, H. U.; Schade, W.; Amombo, M.
O.; Pulz, R.; Hausherr, A. Pure Appl. Chem. 2002, 175; (i) Ma, S. Carbopalladation
of Allenes. In Handbook of Organopalladium Chemistry for Organic Synthesis;
Negishi, E., Ed.; Wiley-Interscience: NewYork, 2002; p 1491.
3. Selected reviews on methylenecyclopropanes: (a) Brandi, A.; Goti, A. Chem. Rev.
1998, 98, 589; (b) Brandi, A.; Cicchi, S.; Cordero, F. M.; Goti, A. Chem. Rev. 2003,
103, 1213; (c) Nakamura, I.; Yamamoto, Y. Adv. Synth. Catal. 2002, 344, 111.
4. (a) Yu, L.; Meng, B.; Huang, X. Synlett 2007, 2919; (b) Yu, L.; Meng, B.; Huang, X.
Synlett 2008, 1331; (c) Yu, L.; Meng, B.; Huang, X. J. Org. Chem. 2008, 73, 6895.
5. Select recent article about difunctional reactions: (a) Morgan, J. B.; Miller, S. P.;
Morken, J. P. J. Am. Chem. Soc. 2003, 125, 8702; (b) Rauhut, C. B.; Melzig, L.;
Knochel, P. Org. Lett. 2008, 10, 3891; (c) Shi, M.; Jiang, M.; Liu, L.-P. Org. Biomol.
Chem. 2007, 5, 438.
6. Siriwardana, A. I.; Nakamura, I.; Yamamoto, I. Tetrahedron Lett. 2003, 44, 985.
7. Selected recent articles about conjugated dienes: (a) Zhou, C.; Fu, C. L.; Ma, S.
M. Tetrahedron 2007, 63, 7612; (b) Shi, M.; Wang, B. Y.; Huang, J. W. J. Org.
Chem. 2005, 70, 5606; (c) Wong, K.; Hung, Y. Tetrahedron Lett. 2003, 44, 8033;
(d) Taylor, D. K.; Avery, T. D.; Greatrex, B. W.; Tiekink, E. R. T.; Macreadie, I. G.;
Macreadie, P. I.; Humphries, A. D.; Kalkanidis, M.; Fox, E. N.; Klonis, N.; Tilley, L.
J. Med. Chem. 2004, 47, 1833.
8. Selected recent articles about homoallylic compounds: (a) Shi, M.; Xu, B. Org.
Lett. 2002, 4, 2145; (b) Xu, B.; Shi, M. Org. Lett. 2003, 5, 1415; (c) Liu, L. P.; Shi,
M. J. Org. Chem. 2004, 69, 2805; (d) Huang, J. W.; Shi, M. Tetrahedron 2004, 60,
2057; (e) Huang, X.; Yu, L. Synlett 2005, 2953; (f) Chen, Y.; Shi, M. J. Org. Chem.
2004, 69, 426; (g) Huang, J. W.; Shi, M. Tetrahedron Lett. 2003, 44, 9343; (h)
Shao, L. X.; Huang, J. W.; Shi, M. Tetrahedron 2004, 60, 11895; (i) Zhou, H. W.;
Huang, X.; Chen, W. L. Synlett 2003, 2080.
E+
E
E
R2
H
E
C
=
R1
Nu
R2
R1
R1
R1
R2
R2
1
5
5 (A)
Nu-
R2
E
R2
H
R2
H
E
E
R1
=
H
R1
4 (1Z 3Z)
H
R1
H
5 (B)
Scheme 2. Proposed mechanism for the reaction.
Ph
I
Ph
Br
Br
Pd(PPh3)2Cl2, CuI, Et3N
Ph
Ph
4a
6
90%
NaBH4
(PhSe)2
93%
I
Ph
PhB(OH)2
Pd(PPh3)4, K3PO4 3H2O
74%
.
PhSe
PhSe
Ph
Ph
8
7
Scheme 3. The synthetic utilities of Z-4a.
9. Negishi, E.; de Meijere, A., et al Organopalladium Chemistry for Organic Synthesis;
Wiley: New York, 2002. pp 493–529, and references cited therein.
10. (a) Hopf, H.; Jager, H.; Ernst, L. Liebigs Ann. 1996, 815; (b) Kros, A.; Nolte, R. J.
M.; Sommerdijk, N. A. J. M. Adv. Mater. 2002, 14, 1779; (c) Carroll, R. L.;
Gorman, C. B. Angew. Chem., Int. Ed. 2002, 41, 4378; (d) McQuade, D. T.; Pullen,
A. E.; Swager, T. M. Chem. Rev. 2000, 100, 2537; (e) Tour, J. M. Acc. Chem. Res.
2000, 33, 791; (f) Liphardt, M.; Goonesekera, A.; Jones, B. E.; Ducharme, S.;
Takacs, J. M.; Zhang, L. Science 1994, 263, 367; (g) Miller, J. S. Adv. Mater. 1993,
5, 671; (h) Greenham, N. C.; Moratti, S. C.; Bradley, D. D. C.; Friend, R. H.;
Holmes, A. B. Nature 1993, 365, 628; (i) Nalwa, H. S. Adv. Mater. 1993, 5, 341; (j)
Buckley, A. Adv. Mater. 1992, 4, 153.
11. (a) Michinobu, T.; Boudon, C.; Gisselbrecht, J. P.; Seiler, P.; Frank, B.; Moonen, N.
N. P.; Gross, M.; Diederich, F. Chem. Eur. J. 2006, 12, 1889; (b) Pahadi, N. K.;
Camacho, D. H.; Nakamura, I.; Yamamoto, Y. J. Org. Chem. 2006, 71, 1152; (c)
Michinobu, T.; May, J. C.; Lim, J. H.; Boudon, C.; Gisselbrecht, J. P.; Seiler, P.;
Gross, M.; Biaggio, I.; Diederich, F. Chem. Commun. 2005, 737.
Containing both a conjugated diene structural unit and a homo-
allylic structural unit, 4 might be of potential value in organic syn-
thesis.7,8 Moreover, the functional groups on 2- or 6-position of 4
allowed it to be easily transformed to some other useful skeletons
(Scheme 3). For example, the Sonogashira coupling9 of 4a with al-
kyne would give the alkynyl-substituted conjugated diene 6 in
good yield. Compound 7 was generated through nucleophilic sub-
stitution of 4a in the presence of NaBH4 and (PhSe)2, and could fur-
ther occur Suzuki coupling to give 8 in 74% yield. All of these
analogs are important organic compounds in part due to their
applications in Diels–Alder reactions and exploration of materials
for electronic and photonic applications,10 and in part due to their
existence in many chromophores as a substructure.11
In conclusion, we reported the difunctional additions of 1-
cyclopropylallenes. The selectivity of this reaction was good and
two different functional groups could be introduced at the same
time. This would provide an efficient and stereospecific method
for the synthesis of 2,6-difunctional-1,3-hexadienes.12 Further
investigations on 1-cyclopropylallenes are being undertaken in
our laboratory.
12. Typical procedure of Synthesis of 2,6-dihalo-1,3-hexadienes 4: In a Schlenk tube,
0.3 mmol of 1 was dissolved in 2 mL of THF under nitrogen atmosphere. Then,
0.3 mmol of NXS and MY (metal halides) were added. The mixture was stirred
at room temperature and the reaction was monitored by TLC (eluent:
petroleum ether). When the reaction terminated, the solvent was evaporated
under vacuum, and the residue was isolated by preparation TLC (eluent:
petroleum ether) to give the corresponding product 4. Selected spectroscopic
data of compound 4a: Oil. IR (film): 3023, 2959, 1603, 1445, 1105, 965, 761,
694 cmÀ1
.
1H NMR (400 MHz, CDCl3, TMS): d 7.41 (d, J = 6.8 Hz, 2H), 7.30–7.35
(m, 3H), 6.22 (s, 1H), 6.19 (s, 1H), 5.87 (t, J = 7.2 Hz, 1H), 3.47 (t, J = 6.8 Hz, 2H),
2.84 (q, J = 6.8 Hz, 2H). 13C NMR (100 MHz, CDCl3): d 31.3, 32.8, 102.6, 125.5,
126.6, 128.1, 128.4, 130.7, 137.3, 146.3. MS (EI, 70 eV): m/z (%) 362 (25) [M+],
156 (100). HRMS (EI): m/z calcd for C12H12BrI: 361.9167; found: 361.9165.
Selected spectroscopic data of compound 5a: Oil. IR (film): 2973, 2864, 1604,
1446, 1375, 1109, 907, 763 cmÀ1 1H NMR (400 MHz, CDCl3, TMS): d 7.44–7.45
.
Acknowledgments
(m, 2H), 7.31–7.38 (m, 3H), 6.25 (s, 1H), 6.22 (s, 1H), 5.96 (t, J = 7.2 Hz, 1H),
3.51–3.59 (m, 4H), 2.59 (t, J = 7.2 Hz, 2H), 1.24 (t, J = 7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3): d 15.2, 30.6, 66.2, 69.3, 103.2, 125.9, 126.6, 127.8, 128.3,
130.5, 137.8, 145.3. MS (EI, 70 eV): m/z (%) 328 (7) [M+], 115 (100). HRMS (EI):
We are grateful to the National Natural Science Foundation of
China (Project Nos. 20732005 and 20872127), National Basic

1950
B. Meng et al. / Tetrahedron Letters 50 (2009) 1947–1950
m/z calcd for C14H17IO: 328.0324; found: 328.0316. Selected spectroscopic data
of compound 6: Oil. IR (film): 2922, 1724, 1490, 1241, 1172, 913, 756 cmÀ1 1H
130.0, 130.4, 132.7, 137.5, 145.0. MS (EI, 70 eV): m/z (%) 440 (2) [M+], 313
.
(100). HRMS (EI): m/z calcd for C18H17ISe: 439.9540; found: 439.9544.
Spectroscopic data of Compound 8: Oil. IR (film): 2963, 1588, 1432, 1311,
NMR (400 MHz, CDCl3, TMS): d 7.48–7.50 (m, 2H), 7.34–7.37 (m, 4H), 7.26–
7.32 (m, 4H), 5.88–5.91 (m, 2H), 5.46 (s, 1H), 3.28 (t, J = 7.2 Hz, 2H), 2.99 (q,
J = 7.2 Hz, 2H). 13C NMR (100 MHz, CDCl3): d 5.0, 33.5, 89.3, 89.9, 122.9, 126.7,
127.1, 127.6, 128.2, 128.3, 128.3, 128.5, 129.0, 131.6, 140.0, 141.6. MS (EI,
70 eV): m/z (%) 336 (20) [M+], 105 (100). HRMS (EI): m/z calcd for C20H17Br:
336.0514; found: 336.0508. Spectroscopic data of Compound 7: Oil. IR (film):
1125, 1094, 887, 775 cmÀ1 1H NMR (400 MHz, CDCl3, TMS): d 7.49–7.51 (m,
.
2H), 7.44–7.46 (m, 2H), 7.29–7.34 (m, 5H), 7.26–7.28 (m, 3H), 7.22–7.23 (m,
3H), 5.86 (t, J = 7.2 Hz, 1H), 5.52 (s, 1H), 5.38 (s, 1H), 2.84 (t, J = 7.6 Hz, 2H), 2.61
(q, J = 7.2 Hz, 2H). 13C NMR (100 MHz, CDCl3): d 27.1, 30.6, 117.9, 126.6, 126.8,
127.5, 128.1, 128.2, 128.5, 129.0, 129.1, 129.2, 130.2, 132.6, 136.6, 139.0, 140.0,
141.7. MS (EI, 70 eV): m/z (%) 390 (12) [M+], 235 (100). HRMS (EI): m/z calcd for
C24H22Se: 390.0887; found: 390.0882. Spectroscopic data of the other
compounds please see the Supplementary data file.
2936, 1598, 1411, 1207, 985, 764 cmÀ1 1H NMR (400 MHz, CDCl3, TMS): d
.
7.58–7.61 (m, 2H), 7.30–7.45 (m, 8H), 6.19 (s, 1H), 6.18 (s, 1H), 5.95 (t,
J = 7.6 Hz, 1H), 3.08 (t, J = 7.2 Hz, 2H), 2.76 (q, J = 7.2 Hz, 2H). 13C NMR
(100 MHz, CDCl3): d 26.2, 30.3, 102.9, 126.5, 126.8, 127.6, 127.8, 128.3, 129.0,