Solvent free synthesis of 1-alkoxyphosphonium chlorides for stereoselective multipurpose vinyl ethers

Article abstract of DOI:10.1080/10426507.2019.1633533

An efficient solvent free method is developed for the preparation of structurally diverse 1-alkoxymethylphosphonium chlorides in high yield. One of the prepared salts derived from (1 R,2S,5R)-(?)-Menthol auxiliary was further employed for the synthesis of vinyl ethers, where up to 99% stereoselectivity was achieved.

Full text of DOI:10.1080/10426507.2019.1633533

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: https://www.tandfonline.com/loi/gpss20
Solvent free synthesis of 1-alkoxyphosphonium
chlorides for stereoselective multipurpose vinyl
ethers
Zain Maqsood Cheema, Humaira Yasmeen Gondal, Hina Siddiqui &
Muhammad Iqbal Choudhary
To cite this article: Zain Maqsood Cheema, Humaira Yasmeen Gondal, Hina Siddiqui &
Muhammad Iqbal Choudhary (2019): Solvent free synthesis of 1-alkoxyphosphonium chlorides
for stereoselective multipurpose vinyl ethers, Phosphorus, Sulfur, and Silicon and the Related
Elements, DOI: 10.1080/10426507.2019.1633533
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PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
https://doi.org/10.1080/10426507.2019.1633533
Solvent free synthesis of 1-alkoxyphosphonium chlorides for stereoselective
multipurpose vinyl ethers
Zain Maqsood Cheemaa, Humaira Yasmeen Gondala, Hina Siddiquib, and Muhammad Iqbal Choudharyb
b
aDepartment of Chemistry, University of Sargodha, Sargodha, Pakistan; H.E.J Research Institute of Chemistry, International Center for
Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
ABSTRACT
ARTICLE HISTORY
Received 18 December 2018
Accepted 14 June 2019
An efficient solvent free method is developed for the preparation of structurally diverse 1-alkoxy-
methylphosphonium chlorides in high yield. One of the prepared salts derived from (1 R,2S,5R)-
(ꢀ)-Menthol auxiliary was further employed for the synthesis of vinyl ethers, where up to 99%
stereoselectivity was achieved.
KEYWORD
Functionalized phosphon-
ium salts;
alkoxymethylphosphonium
salts; bis-alkoxymethane;
alkoxymethyl halides; vinyl
ethers; enol ethers
GRAPHICAL ABSTRACT
1. Introduction
2. Results and discussion
Vinyl ethers are key intermediates in many organic transfor- First part of the current work was to synthesize 1-alkoxyme-
mations like Nazarov cyclization,[1] olefin metathesis,[2] thylphosphonium chlorides through phosphination of methox-
Diels-Alder reaction,[3] coupling reactions,[4] [3 þ 2]-cyclo- ymethyl chloride. In order to optimize reaction conditions, a
addition reactions[5] and Claisen rearrangement.[6] They are series of parameters was screened (Table 1). Early attempts of
also used in material sciences owing to their polymeric abil- reacting equimolar ratio of methoxymethyl chloride 2a and tri-
ity through the cationic mechanism.[7] Vinyl ethers are inte- phenylphosphine in toluene were not very successful at differ-
gral part of many natural products and are also involved in ent temperatures (Table 1, entries 1-4). Replacing toluene with
the total synthesis of some others.[8] Many methodologies acetonitrile was also futile (Table 1, entries 5-7). However,
have been established for the synthesis of vinyl ethers such when the reaction mixture was refluxed in benzene, desired
as metal catalyzed couplings,[9–11] exchange reactions,[12] phosphonium salt 3a was obtained in 4 hours with 73% yield
hydroalkoxylation of acetylenes,[13] silyl enol ethers[14] and (Table 1, entry 8). Yield was further improved to 80% on using
Wittig reaction.[15] Methoxymethyltriphenylphosphonium 1.5 eq of methoxymethyl chloride 2a (Table 1, entry 9). But
chloride 3a is a leading example, which was first synthesized the toxicity of benzene was still bothering us therefore, we
by heating chloromethyl methyl ether 2a and triphenylphos- decided to perform the reaction under solvent free conditions
phine in benzene at 50 ꢁC for 60 hours (Figure 1a).[16–18] and to our delight the required salt 3a was obtained with 95%
Later, Burton et al., reported the same reaction at 70 ꢁC for yield (Table 1, entry 10–11).
15 hours in benzene.[15c] Problems associated with such
The substrate scope of this reaction was extended to a
methods involve: long reaction time (15–60 hours), toxic range of a-alkoxymethyl chlorides 2a-f (see supplementary
solvent (benzene) and tedious procedure for the preparation information).[15a,19] Optimized reaction conditions were
of intermediate 2a.[18] Herein, we report an efficient, solvent found equally effective for primary, secondary and even ter-
free method for the synthesis of methoxymethyltriphenyl- tiary alkoxy groups (3a-f, Table 2). Chiral alkoxymethyl-
phosphonium chloride 3a and its higher analogs (Figure phosphonium salts 3e-f were also obtained in a high yield
1b). The structurally diverse phosphonium salts 3a-h carry- (Table 2, Entry 5-6) with retention of configuration. Here, it
ing primary, secondary and tertiary alkoxy groups are is worth mentioning that we obtained a-menthoxymethyl-
synthesized successfully in
a good yield. (1 R,2S,5R)- phosphonium chloride 3f with 90% yield in just 4 h (Table
(ꢀ)-Menthyloxymethyl phosphonium chloride 3f is further 2, Entry 6) as compared to the previous report where the
employed to prepare vinyl ethers with good stereoselectivity. same salt was synthesized in a much longer time of 15 h.[20]
CONTACT Humaira Yasmeen Gondal
hygondal@yahoo.com
Department of Chemistry, University of Sargodha, Sargodha, 40100, Pakistan.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gpss.
Supplemental data for this article is available online at https://doi.org/10.1080/10426507.2019.1633533.
ß 2019 Taylor & Francis Group, LLC

2
Z. M. CHEEMA ET AL.
Table 1. Optimization of reaction conditions for a-methoxymethylphospho-
nium chloride 3a.
(a) Previous work
O
O
(2a)
Cl
+
MeOH
+
HCl
Me
O
H
H
(1)
Molar Ratio
2a/PPh3
Temp
(ꢁC)
Time
(h)
Yield
(%)
15-60 h
Me
Entry
Solvent Additive
O
Cl + PPh3
Me
Cl
PPh3Cl
(2a)
Benzene
1.
2.
3.
4.
5.
6.
7.
8.
1:1
1:1
1:1
1.5:1
1:1
1:1
1:1
1:1
1.5:1
1:1
1.5:1
PhCH3
PhCH3
PhCH3
PhCH3
CH3CN
CH3CN
CH3CN
C6H6
–
–
–
–
–
–
–
–
–
–
–
Room temp
8
5
8
6
3
6
4
4
4
4
4
No reaction
traces
(3a)
40
110
110
80
40
20
80
80
70
80
(b) This work
20
22
CH3COCl
O
R
O
O
No reaction
No reaction
Traces
73
R
+
R
(1)
(2)
3-4 h
solvent free
O
R
Cl
R
9.
10.
11.
C6H6
–
–
80
82
95
PPh3
O
PPh3 Cl
(2)
(3a-f)
R = Me, Et, n-Bu, t-Bu, s-Bu, Menthyl
1
Materials contains sample H, 13C and 31P NMR spectra of
Figure 1. Synthesis of a-alkoxymethyltriphenylphosphonium chlorides 3a–f.
products 3 and 4 (Figures S1 – S26)
After the successful preparation of 1-alkoxyphosphonium
chlorides, we intended to utilize them for stereoselective
synthesis of vinyl ethers. For this purpose, (1 R,2S,5R)-
(ꢀ)-menthyloxymethyl phosphonium chloride 3f was
reacted with a variety of aldehydes in the presence of n-
BuLi. The diastereomeric ratio of the vinyl ethers obtained
(Figure 2) was calculated by 1H NMR spectroscopy.
Exclusively, trans isomers 4a’ and 4b’ were obtained with
benzaldehyde and 4-bromo benzaldehyde. Similarly, 4-
methoxy benzaldehyde also provided the trans isomer 4c’ as
a major product with dr (31:69), but the selectivity was
decreased (dr 47:53) in case of pyridine-3-carboxaldehyde.
On the other hand, the reversal in selectivity was observed
with furfural and 4-chloro benzaldehyde where cis isomers
4e and 4f were obtained as major products with dr (60:40)
and (77:33) respectively. The diastereomeric mixture was
successfully separated on silica gel column in almost same
ratio of cis 4f and trans 4f’ isomers.
3.2. General procedure for synthesis of a-alkoxymethyl
phosphonium salts (3a-f)
A sealable reaction tube equipped with magnetic bar was
charged with triphenylphosphine (10 mmol) and a-alkoxy-
methyl chloride (15 mmol). The reaction mixture was stirred
at given temperature and time under inert conditions. The
required salts obtained were further purified on silica gel
column eluted with DCM/MeOH (10/1).
3.2.1. (Methoxymethyl)triphenylphosphonium chloride (3a)
White crystalline solid, m.p ¼ 186-189 ꢁC, yield ¼ 93%,
1
IR: t (cmꢀ1) ¼ 691, 724, 1112, 1437, 2877, 2958. H-NMR
(500 MHz, CDCl3): d ppm 7.75-7.70 (9 H, m, C-H aro-
matic), 7.64-7.61 (6 H, m, C-H aromatic), 5.70 (2 H, d,
J ¼ 4 Hz, CH2), 3.51 (3 H, s, CH3). 13C-NMR (125 MHz,
CDCl3): d ppm. 135.2 (d, J ¼ 2.5 Hz, 3 C), 133.8 (d,
J ¼ 10.0 Hz, 6 C), 130.2 (d, J ¼ 12.5 Hz, 6 C), 116.2 (d,
J ¼ 85.0 Hz, 3 C), 65.6 (d, J ¼ 68.0 Hz). 31P (CDCl3): d ppm
17.22. HRMS (ESI) calculated for C20H20OP: 307.1246,
found: 307.1251.[15c,17b]
3. Experimental
3.1. General
All experiments were carried out under inert atmosphere
using standard Schlenk techniques with oven dried glassware
and magnetic stirring. All solvents were freshly dried and
distilled before use. All chemicals were purchased from
Sigma Aldrich, Alfa Aesar and Merck. Reactions were moni-
3.2.2. (Ethoxymethyl)triphenylphosphonium chloride (3b)
Colorless oil: yield ¼ 82%, IR: t (cmꢀ1) ¼ 2846, 2794, 1946,
1586, 1484, 1437, 1317, 1112, 1092; 1H NMR (400 MHz,
CDCl3) d ¼ 7.77-7.70 (9 H, m), 7.65-7.60 (6 H, m), 5.72 (2 H,
d, J ¼ 3.96 Hz), 3.85 (2 H, q, J ¼ 7.0 Hz), 1.09 (3 H, t,
J ¼ 7.0 Hz); 13C NMR (100 MHz, CDCl3) d ¼ 135.3 (d,
J ¼ 2.9 Hz, 3 C), 134.0 (d, J ¼ 9.9 Hz, 6 C), 130.3 (d,
J ¼ 12.6 Hz, 6 C), 128.4 (d, J ¼ 11.3 Hz), 116.5 (d, J ¼ 85.6 Hz,
3 C), 64.21 (d, J ¼ 68.0 Hz), 14.93; 31P-NMR (CDCl3): d 19.0;
HRMS (ESI) calculated for C21H22OP: 321.1403;
found 321.1404.[17b]
tored on TLC plates obtained from Merck (silica gel 60 F254
,
aluminum oxide 60 F254). TLCs were visualized by UV fluor-
escence and phosphomolybdic acid as spraying agent. IR
spectra were measured on a Perkin-Elmer Paragon 1000
(thin film) or on a Perkin-Elmer BXII spectrometer (neat).
Optical rotation was measured on Polarimeter P-2000.
Melting points were recorded on a Gallenkamp hot stage.
Bruker Avance NMR spectrometer of 300 MHz, 400 MHz
and 500 MHz were used for NMR spectra. Mass spectra
3.2.3. (n-butoxymethyl)triphenylphosphonium chloride (3c)
were measured by using Agilent Tech. 6530 LC/MS or Light brown oil, yield ¼ 87%, IR: t (cmꢀ1) ¼ 695, 722,
Agilent Tech. 7200 GC/MS-Q-TOF. The Supplemental 1115, 1310, 1433, 2859. 1H-NMR (300 MHz, MeOD): d

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
3
Table 2. Synthesis of a-alkoxymethytriphenylphosphonium chlorides 3a–f.
Entry
1
2
3
Yield (%)
95
2
3
91
87
4
71
5
6
91
90
R
i) n-BuLi, -78 oC
O
PPh3Cl
R
ii) RCHO, 3h
OR
4a-f
3
Br
MeO
H
C
H
C
H
C
O
O
O
H
H
H
4a´
54%, dr 99:1
4b´
52%, dr 99:1
4c,c´
54%, dr 31:69
Cl
N
H
C
H
C
H
C
O
O
O
O
H
H
H
4d,d´
52%, dr 47:53
4e,e´
50%, dr 60:40
4f,f´
55%, dr 77:33
Figure 2. Stereoselective vinyl ethers from menthoxymethylphosphonium chloride (3f).

4
Z. M. CHEEMA ET AL.
ppm. 7.93-7.91 (2 H, m, CH aromatic), 7.91-7.90 (2 H, m, under argon. After 15-20 minutes solution of aldehyde (1
CH aromatic), 7.90-7.89 (2 H, m, CH aromatic) 7.82-7.80 eq) in THF was added drop wise at the same temperature
(2 H, m, CH aromatic), 7.78-7.76 (5 H, m, CH aromatic), and the reaction mixture was allowed to stir for further
7.76-7.74 (2 H, m, CH aromatic), 5.41 (2 H, d, J ¼ 4.8 Hz, 14 hours allowing to raise the temperature at room tempera-
CH2), 3.72 (2 H, t, J ¼ 6.3 Hz, CH2), 1.59-1.50 (2 H, m, ture. Reaction was monitored by using TLC, on completion,
CH2), 1.29-1.21 (2 H, m, CH2), 0.84 (3 H, t, J ¼ 7.3 Hz,
reaction was quenched with methanol and solvent was
CH3). HRMS (ESI) calculated for C23H26OP: 349.1716,
found: 349.1719.[17c]
evaporated under reduced pressure. Products were purified
on silica gel column chromatography using ethyl acetate: pet
ether as eluent.
3.2.4. (Tert-butoxymethyl)triphenylphosphonium chlor-
ide (3d)
3.3.1. (E)-(2-((2-isopropyl-5-methylcyclohexyl)oxy)vinyl)ben-
Dark brown thick oil, yield ¼ 71%, IR: t (cmꢀ1) ¼ 690,
zene (4a’)
1
1
713, 1127, 1295, 1405, 2799. H-NMR (300 MHz, MeOD): d
Colorless oil; yield ¼ 54%, H NMR (CDCl3, 400 MHz): d
ppm 7.91-7.89 (3 H, m, CH aromatic), 7.88-7.80 (4 H, m,
CH aromatic), 7.79-7.75 (2 H, m, CH aromatic), 7.34-7. 31
(2 H, m, CH aromatic), 7.25-7.23 (4 H, m, CH aromatic),
5.44 (2 H, d, J ¼ 4.8 Hz, CH2), 0.047 (9 H, s, CH3). 13C NMR
(100 MHz, CDCl3) d ¼ 135.5 (d, J ¼ 3.0 Hz, 3 C), 133.8 (d,
J ¼ 6.0 Hz, 6 C), 130.5 (d, J ¼ 12.0 Hz, 6 C), 116.8 (d,
J ¼ 86.0 Hz, 3 C), 83.8, 31.6 (3 C); 31P-NMR (CDCl3): d
17.08; HRMS (ESI) calculated for C23H26OP: 349.1716,
found: 349.1718.
ppm 7.28-7.22 (4 H, m), 7.15-7.11 (1 H, m), 6.92 (1 H, d,
J ¼ 12.6 Hz), 5.93 (1 H, d, J ¼ 12.6 Hz), 3.62 (1 H, td,
J ¼ 4.3 Hz), 2.21-2.10 (2 H, m), 1.72-1.71(1H, m), 1.69-1.68
(1 H, m), 1.58-1.52 (1 H, m), 1.49-1.39 (2 H, m), 1.11-1.01
(2 H, m), 0.95 (3 H, d, J ¼ 6.1 Hz), 0.94 (3 H, d, J ¼ 6.6 Hz),
0.82 (3 H, d, J ¼ 6.9 Hz); 13C NMR (CDCl3, 100 MHz): d
ppm 147.5, 136.7, 128.6 (2 C), 125.4 (2 C), 124.9, 107.0, 81.6,
47.8, 41.4, 34.3, 31.5, 25.8, 23.4, 22.1, 20.7, 16.4. HRMS (ESI)
calculated for C18 H26O; 258.1984, found; 258.1987.[15a]
3.2.5. (S)-(sec-butoxymethyl)triphenylphosphonium chlor-
ide (3e)
3.3.2. 1-bromo-4-[(1E)-2-[(2-isopropyl-5-methylcyclohexyl)
oxy]ethenyl]benzene (4b’)
Colorless oil; yield ¼ 56%, ½aꢂD ¼ þ10.9 (c ¼ 0.030, CHCl3),
Lemon yellow oil, yield ¼ 91%, IR: t (cmꢀ1) ¼ 694, 721,
25
25
1114, 1309, 1437, 2861. ½aꢂD ¼ –37.0 (0.05, CHCl3), 1H-
IR: t (cmꢀ1) ¼ 2911, 2168, 2042, 1654, 1584, 1343, 1095,
1044. 1H NMR (CDCl3, 400 MHz): d ppm 7.37 (2 H, d,
J ¼ 8.5 Hz), 7.09 (2 H, d, J ¼ 8.5 Hz), 6.91 (1 H, d,
J ¼ 12.6 Hz), 5.86 (1 H, d, J ¼ 12.6 Hz), 3.61 (1 H, td, J ¼ 10.9,
4.4 Hz), 2.19-2.08 (2 H, m), 1.72-1.67 (2 H, m), 1.46-1.35
(2 H, m), 1.33-1.31 (1 H, m), 1.10-1.06 (1 H, m), 1.04-1.00
(1 H, m), 0.95 (3 H, d, J ¼ 6.5 Hz), 0.93 (3 H, d, J ¼ 7.2 Hz),
0.82 (3 H, d, J ¼ 7.0 Hz); 13C NMR (CDCl3, 100 MHz): d
ppm 148.0, 131.5, 128.6 (2 C), 126.4 (2 C), 124.9, 105.9, 81.8,
47.7, 41.3, 34.2, 31.5, 25.8, 23.4, 22.0, 20.6, 16.3; HRMS
(ESI) calculated for C18H25OBr; 336.1083, found; 336.1080.
NMR (300 MHz, MeOD): d ppm. 7.91-7.89 (3 H, m, CH
aromatic), 7.88-7.81 (3 H, m, CH aromatic), 7.78-7.74 (7 H,
m, CH aromatic), 7.73-7.72 (2 H, m, CH aromatic), 5.49
(1 H, dd, J ¼ 4.8, 13.5 Hz, CH2), 5.35 (1 H, dd, J ¼ 5.7 Hz,
13.5, CH2), 3.67-3.61 (1 H, m, CH), 1.57-1.45 (2 H, m, CH2),
1.17 (3 H, d, J ¼ 6.0 Hz, CH3), 0.75 (3 H, t, J ¼ 7.5, CH3). 13C
NMR (100 MHz, CDCl3) d ¼ 134.0 (d, J ¼ 16 Hz, 3 C), 132.0
(d, J ¼ 8 Hz, 6 C), 128.5 (d, J ¼ 5.0 Hz, 6 C), 93.9, 91.3, 69.5,
29.7, 9.4; 31P-NMR (CDCl3): d 18.96; HRMS (ESI) calculated
for C23H26OP (Mþ): 349.1716, found: 349.1717.
3.2.6. ((((1S,2R,5S)-2-isopropyl-5-methylcyclohexyl)oxy)
methyl)triphenylphosphonium chloride (3f)
3.3.3. 1-[(1E & Z)-2-[(2-isopropyl-5-methylcyclohexyl)oxy]
ethenyl]-4-methoxybenzene (4c & c’)
Yellowish white solid, yield ¼ 89%, IR: t (cmꢀ1) ¼ 690,
(mixture of cis and trans isomers) Colorless oil; yield ¼ 54%,
25
IR: t (cmꢀ1) ¼ 2924, 2160, 2030, 1572, 1606, 1424, 1370,
748, 1113, 1311, 1437, 2812. ½aꢂD ¼ ꢀ1763 (c ¼ 0.005,
MeOH), 1H NMR (400 MHz, CDCl3) d ¼ 7.84–7.79 (3 H,
m), 7.72–7.67 (12 H, m), 5.44 (1 H, dd, J ¼ 13.5, 3 Hz),
5.12 (1 H, dd, J ¼ 13.5, 3.6 Hz), 3.48–3.39 (1 H, m),
2.26–2.13 (2 H, m), 1.95–1.92 (1 H, m), 1.66–1.52 (2 H,
m), 1.42–1.36 (2 H, m), 1.25–1.06 (2 H, m), 0.78 (3 H, d,
J ¼ 7.0 Hz), 0.70 (3 H, d, J ¼ 7.0 Hz), 0.50 (3 H, d,
J ¼ 7.0 Hz). HRMS (ESI) calculated for C29H36OP:
431.2498; found: 431.2513.[20]
1
1082, 1027. H NMR (CDCl3, 400 MHz): d ppm 7.57 (0.6 H,
d, J ¼ 9.5 Hz), 7.17-7.15 (1.4 H, m), 6.86-6.82 (2 H, m), 6.81
(0.69 H, d, J ¼ 15.8 Hz), 6.20 (0.31 H, d, J ¼ 8.8 Hz), 5.93
(0.69 H, d, J ¼ 15.8 Hz), 5.16 (0.31 H, d, J ¼ 8.8 Hz), 3.81
(3 H, s), 3.62-3.51 (1 H, m), 2.25-2.07 (2 H, m), 1.72-1.68
(2 H, m), 1.62-1.45 (1 H, m), 1.44-1.40 (1 H, m), 1.16-1.01
(2 H, m), 0.96 (3 H, d, J ¼ 7.3 Hz), 0.94 (3 H, d, J ¼ 7.7 Hz),
0.92-0.89 (1 H, m), 0.84 (6 H, d, J ¼ 8.6 Hz); 13C NMR
(CDCl3, 100 MHz): d ppm 157.6 (2 C), 146.0, 144.6, 129.4
(2 C), 129.3 (2 C), 129.1 (2 C), 125.9 (2 C), 114.0, 113.5,
106.6, 104.3, 83.4, 81.3, 77.2, 55.3, 55.2, 47.9, 47.8, 41.9, 41.3,
3.3. General method for synthesis of vinyl ethers 4a-g
In a flame dried two neck round bottom flask n-BuLi (2.2 34.3 (2 C), 31.6, 31.5, 29.7, 25.9, 25.8, 23.5 (2 C), 22.1, 20.9,
eq) was added to a stirred solution of phosphonium chloride 20.7, 16.3 (2 C); HRMS (ESI) calculated for C19H28O2;
(1 eq) in THF at -78 ꢁC and the mixture was allowed to stir 288.2084, found; 288.2098.

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
5
3.3.4. 3-[(1E)-2-[(2-isopropyl-5-methylcyclohexyl)oxy]ethenyl] 3.3.7. 1-chloro-4-[(1E)-2-[(2-isopropyl-5-methylcyclohexyl)oxy]
ethenyl]benzene (4f’)
pyridine (4d & d’)
25
Colorless oil; yield ¼ 11%, ½aꢂD ¼ þ71.0 (c ¼ 0.020, CHCl3),
(mixture of cis and trans isomers) Colorless oil; yield ¼ 52%,
IR: t (cmꢀ1) ¼ 2923, 2155, 2031, 1659, 1632, 1585, 1309,
IR: t (cmꢀ1) ¼ 2933, 2159, 2055, 1572, 1613, 1454, 1370,
1
1
1175, 1084, 1038 . H NMR (CDCl3, 400 MHz): d ppm 7.23-
1086, 1023. H NMR (CDCl3, 400 MHz): d ppm 7.55-7.42
7.20 (2 H, m), 7.16-7.13 (2 H, m), 6.90 (1 H, d, J ¼ 12.6 Hz),
5.88 (1 H, d, J ¼ 12.6 Hz), 3.01 (1 H, td, J ¼ 10.7, 4.4 Hz),
2.15-2.09 (2 H, m), 1.73-1.68 (2 H, m), 1.46-1.38 (1 H, m),
1.25-1.18 (1 H, m), 1.11-1.01 (2 H, m), 0.95 (3 H, d,
J ¼ 6.4 Hz), 0.92 (3 H, d, J ¼ 6.2 Hz), 0.82 (3 H, d, J ¼ 7.0 Hz);
13C NMR (CDCl3, 100 MHz): d ppm 147.9, 135.3, 130.9,
129.4(2 C), 128.6(2 C), 126.0, 105.9, 81.8, 47.7, 41.3, 34.2,
31.5, 25.8, 23.4, 22.1, 20.7, 16.3; HRMS (ESI) calculated for
C18H25OCl; 292.1588, found; 292.1596.
(3 H, m), 7.22-7.15 (1 H, m), 6.97 (0.53 H, d, J ¼ 15.9 Hz),
6.40 (0.47 H, d, J ¼ 8.7 Hz), 5.88 (0.53 H, d, J ¼ 15.9 Hz), 5.17
(0.47 H, d, J ¼ 8.7 Hz), 3.66 (0.48 H, dt, J ¼ 11.0, 4.5 Hz), 3.15
(0.53 H, dt, J ¼ 10.6, 4.6 Hz), 2.17-2.06 (2 H, m), 1.74-1.68
(2 H, m), 1.56-1.47 (1 H, m), 1.37-1.30 (1 H, m), 1.14-1.01
(2 H, m), 0.97 (1.2 H, d, J ¼ 3.0 Hz), 0.95 (1.7 H, d,
J ¼ 3.1 Hz), 0.91 (2.6 H, d, J ¼ 6.3 Hz), 0.83 (1.5 H, d,
J ¼ 2.3 Hz), 0.82 (1.6 H, d, J ¼ 2.1 Hz), 0.76 (1.4 H, d,
J ¼ 7.0 Hz); 13C NMR (CDCl3, 100 MHz): d ppm 149.1,
148.8, 148.2, 146.6, 146.5, 146.0, 134.6, 132.6, 132.4, 131.6
(2 C), 131.5, 131.4, 131.3, 130.8, 128.5, 128.4, 128.3 (2 C),
128.2, 123.3, 123.1; 103.2, 101.1, 103.2, 101.1, 84.2, 82.0,
77.2, 73.3, 48.0, 47.8, 47.7, 41.9, 41.3, 40.9, 39.2, 34.3, 34.2
(2 C), 33.8, 31.6, 31.5, 31.4, 29.7, 28.4, 26.0, 25.9, 25.1, 23.9,
23.4, 22.9, 22.2, 22.1, 20.9, 20.8, 20.7, 17.5; HRMS (ESI) cal-
culated for C17H25NO; 260.2009, found; 260.0409.
4. Conclusion
A facile, efficient and solvent free strategy for the synthesis
of 1-alkoxymethyl phosphonium chlorides has been
designed. Generalization of the reaction is established to
synthesize structurally diverse a-alkoxy substituted phos-
phonium salts. Application of this class of functionalized
phosphonium salts in the synthesis of vinyl ethers has also
been demonstrated where structurally unique chiral vinyl
ethers are obtained with good selectivity.
3.3.5. 2-[(1E)-2-[(2-isopropyl-5-methylcyclohexyl)oxy]ethenyl]
furan (4e-e0)
(mixture of cis and trans isomers) Colorless oil; yield ¼ 50%,
1
IR: t (cmꢀ1) ¼ 2917, 2147, 2051, 1565, 1634, 1084, 1054. H
Acknowledgement
NMR (CDCl3, 400 MHz): d ppm 7.28-7.25 (1 H, m), 6.96
(0.4 H, d, J ¼ 12.7 Hz), 6.54 (0.6 H, d, J ¼ 3.3 Hz), 6.41-6.40
(0.6 H, m), 6.34-6.33 (0.4 H, m), 6.25 (0.6 H, d, J ¼ 6.9 Hz),
5.99 (0.4 H, d, J ¼ 3.2 Hz), 5.79 (0.4 H, d, J ¼ 12.7 Hz), 5.36
(0.6 H, d, J ¼ 6.9 Hz), 3.63 (1 H, dt, J ¼ 10.7, 4.2 Hz), 2.21-
2.07 (2 H, m), 1.74-1.67 (2 H, m), 1.48-1.40 (2 H, m), 1.18-
1.08 (1 H, m), 1.07-1.00 (1 H, m), 0.96 (6 H, d, J ¼ 6.5 Hz),
0.92-0.85 (1 H, m), 0.83 (3 H, d, J ¼ 6.8 Hz); 13C NMR
(CDCl3, 100 MHz): d ppm 152.0, 151.5, 147.4, 144.5, 139.9,
139.3, 111.3, 111.0, 107.2, 103.7, 97.0, 95.3, 83.5, 81.8, 47.9,
47.7, 41.9, 41.2, 34.3, 34.2, 31.6, 31.5, 25.9, 23.5, 23.4, 22.1,
20.8, 20.7, 16.4; HRMS (ESI) calculated for C16H24O2;
248.1771, found; 248.1780.
Authors are highly obliged to Pakistan Science Foundation (PSF),
Islamabad for the support of this research project (P-US/Chem 427).
Disclosure statement
No potential conflict of interest was reported by the authors.
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