Synthesis of Functionalised 3-Isochromanones by Silylcarbocyclisation/Desilylation Reactions

Article abstract of DOI:10.1002/ejoc.201700455

A new protocol for the synthesis of 3-isochromanone derivatives based on rhodium-promoted silylcarbocyclisation reactions of ethynylbenzyl alcohol with different arylsilanes is described. The structure of the isochromanone depends upon the reaction condit

Full text of DOI:10.1002/ejoc.201700455

A Journal of
Accepted Article
Title: A New Synthesis of Functionalised 3-Isochromanones via
Silylcarbocyclisation-Desilylation reactions
Authors: Gianlugi Albano, Martina Morelli, and Laura Antonella Aronica
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10.1002/ejoc.201700455
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A New Synthesis of Functionalised 3-Isochromanones via
Silylcarbocyclisation-Desilylation reactions
Gianluigi Albano[a], Martina Morelli[a] and Laura Antonella Aronica*[a]
Abstract: In this study, a new protocol for the synthesis of 3-
isochromanone derivatives based on rhodium promoted
silylcarbocyclisation reactions of ethynylbenzyl alcohol with different
arylsilanes, is described. The structure of the isochromanone
depends upon the experimental conditions employed: when the
reaction is performed without base (Z)-4-((dimethyl(aryl)silyl)
methylene)isochroman-3-ones are obtained as principal products.
These compounds can be submitted to a desilylation/arylmigration
reaction which generates 4-(methylaryl)isochroman-3-ones in high
yields. On the contrary, in the presence of DBU, hydrogenation of
methyleneisochroman-3-ones takes place and the corresponding β-
silylmethyl-3-isochromanones are formed. Moreover, when internal
alkynes are reacted with hydrosilane under silylcarbocyclisation
reaction conditions, alcoholysis of hydrosilanes exclusively occurs.
cyclocarbonylation of 2-alkynylbenzylalcohol under water-gas shift
reactions conditions (CO+H2O); unfortunately severe experimental
conditions were required (175°C and 100 atm CO)5.
Recently we reported6 that β-lactams and β-lactones can be
easily obtained starting from propargyl amides and propargyl
alcohols by means of rhodium catalysed silylcarbocyclisation
reactions7 (Scheme 2, a). Subsequently, the silylmethylene
group can be submitted to further transformations such as
fluoride promoted 1,2-aryl migration from the silyl moiety to the
adjacent carbon atom followed by a desilylation step6 (Scheme 2,
b).
Introduction
3-Isochromanone derivatives are important intermediates for the
synthesis of pharmaceutical and agrochemical products, as
reported in several patents1. Therefore many efforts have been
directed toward the preparation of such compounds. The main
synthetic approaches to the lactone ring are based on Baeyer-
Villiger oxidation of cyclopentanone2, tandem electrocyclic-
sigmatropic reaction (ECR) of benzocyclobutanes3, and
palladium-catalysed carbonylation of benzyl haloalcohols or α,α’-
dihalides4 (Scheme 1). In the last case, deep mechanistic
investigations were reported by Lindsell and coworkers4i,j, but
the method was applied only to the synthesis of 3-
isochromanone itself.
Scheme 2. Silylcarbocyclisation/desilylation of propargyl alcohols and amides.
Encouraged by these results, we decided to investigate the
application of this cyclisation/desilylation sequence to the
synthesis of 4-methylaryl-3-isochromanones (Scheme 3) whose
preparations and transformations are seldom described in the
literature8.
Scheme 3. Possible synthesis of 3-isochromanones.
Results and Discussion
At the beginning of our study, the silylcarbocyclisation reaction
of 2-ethynylbenzyl alcohol 1 was investigated and the obtained
results are summarized in Table 1. Requisite starting material 1
was easily prepared by Sonogashira reaction of 2-
iodobenzylalcohol 2 followed by desilylation of the acetylenic
moiety of 3 (Scheme 4).
Scheme 1. Main synthetic pathways to 3-isochromanones.
On the contrary, Takahashi and coll. described the synthesis of
several functionalised 3-isochromanones through rhodium promoted
[a]
Dipartimento di Chimica e Chimica Industriale
University of Pisa
Via G. Moruzzi 13, 56124 Pisa, Italy
Fax: (+)390502219260
E-mail: laura.antonella.aronica@unipi.it
Scheme 4. Synthesis of (2-ethynylphenyl)methanol 1.
Supporting information for this article is given via a link at the end of
the document
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10.1002/ejoc.201700455
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Table 1. Silylcarbocyclisation reactions of 2-ethynylbenzylalcohol 1.
entry[a]
Ar
4
DBU
Catalyst
Mol
%
T
(°C)
T
(h)
PCO
(atm)
conv. [b]
5,6,7,8
5[c]
6[c]
7+8[c]
1
Ph
a
a
a
a
a
a
a
a
a
a
a
b
b
c
d
10%
Rh4(CO)12
0.1
0.1
0.1
1
100
100
70
2
30
30
30
30
30
30
30
50
50
50
30
50
50
50
50
90
a
a
a
a
a
a
a
a
a
a
a
b
b
c
d
24
76
/
2
Ph
10%
Rh4(CO)12
4
100
100
100
60
22
78
/
3
Ph
10%
Rh4(CO)12
4
27 (10)
24
73 (67)
/
4
Ph
10%
Rh4(CO)12
100
100
100
30
2
76
/
5
Ph
10%
Rh+[(C7H8)(BPh4)]-
Rh4(CO)12
0.1
0.1
0.1
0.1
1
2
33
67
/
6
Ph
/
/
/
/
/
/
/
/
/
/
2
100
100
100
100
80
54 (42)
51
12 (7)
34 (20) [d]
41[d]
7
Ph
Rh4(CO)12
24
24
24
28
2
8
8
Ph
Rh4(CO)12
30
56
8
36[d]
9
Ph
Rh4(CO)12
30
/
/
100[e]
32[d]
10
11
12
13
14
15
Ph
Rh+[(C7H8)(BPh4)]-
Rh+[(C7H8)(BPh4)]-
Rh4(CO)12
0.1
0.1
0.2
0.2
0.2
0.2
30
60
8
Ph
100
100
100
100
100
85
65
17
18[d]
4-MePh
4-MePh
1-Naptht
4-PhPh
2
100
100
90
39
7
54[f]
Rh+[(C7H8)(BPh4)]-
Rh+[(C7H8)(BPh4)]-
Rh+[(C7H8)(BPh4)]-
4
65 (50)
74 (60)
67 (61)
5
30(20)[f]
12 (8) [g]
20 (7) [h]
4
14 (4)
13 (4)
6
100
[a] Reactions were performed with 3 mmol of alcohol 1, 3 mmol of aryldimethylsilane 4 and 3 mL of CH2Cl2. [b] Conversions were evaluated by GC and 1H
NMR spectroscopic analysis. [c] Selectivity was estimated by 1H NMR spectroscopy; isolated yields of pure products are reported in parentheses. [d] Unless
otherwise stated, a mixture of (E)-(2-(2-(dimethyl(phenyl)silyl)vinyl)phenyl)methanol 7a and (2-(1-(dimethyl(phenyl)silyl)vinyl)phenyl)methanol 8a (ca. 65/35-
75/25) was obtained. [e] A mixture of (E)-(2-(2-(dimethyl(phenyl)silyl)vinyl)phenyl)methanol7a (48%), (2-(1-(dimethyl(phenyl)silyl)vinyl)phenyl)methanol 8a
(34%) and (Z)-(2-(2-(dimethyl(phenyl)silyl)vinyl)phenyl)methanol 9a (18%) was exclusively formed. [f]
tolyl)silyl)vinyl)phenyl)methanol 7b and (2-(1-(dimethyl(p-tolyl)silyl)vinyl)phenyl)methanol 8b (66/34) was obtained. [g]
A
mixture of (E)-(2-(2-(dimethyl(p-
mixture of (E)-(2-(2-
A
(dimethyl(naphthalen-1-yl)silyl)vinyl)phenyl)methanol 7c and (2-(1-(dimethyl(naphthalen-1-yl)silyl)vinyl)phenyl)methanol 8c (85/15) was obtained.[h] Only
(E)-(2-(2-([1,1'-biphenyl]-4-yldimethylsilyl)vinyl)phenyl)methanol 7d was formed.
When 2-ethynylbenzyl alcohol
1
was reacted with
Surprisingly, when the silylcarbocyclization reaction was carried
out in the absence of DBU (Table 1, entry 6) a significant
dimethylphenylsilane 4a under typical silylcarbocyclisation
experimental conditions6, (i.e. 100°C, for 2-4hs, 30 atm CO,
DBU 10mol %, Rh4(CO)12 ), (Table 1, entries 1-2), only a small
amount of desired product 5a was obtained together with large
quantities of 4-((dimethyl(phenyl)silyl)methyl)isochroman-3-one
6a. The same trend was observed performing the reactions at
lower temperature (70°C), or with a larger amount of catalyst
(1mol %) (Table 1, entries 3-4). The unexpected formation of 6a
can be explained considering that a mole of hydrogen is
generated during the reaction9: in the presence of Rh4(CO)12
addition of H2 to the double bond of 5a may occur. Thus,
Rh4(CO)12 was replaced with Rh+[(C7H8)(BPh4)]- (Rhsw), an air
stable zwitterionic species usually employed in silylformylation
reactions10. In this case a light increase in the formation of the
unsaturated product 5a was detected (Table 1, entry 5 vs. 1-4)
together with a lower reagents conversion.
improvement in the chemoselectivity towards
(Z)-4-
((dimethyl(phenyl)silyl)methylene)isochroman-3-one 5a was
observed, even if a considerable amount of hydrosilylation
byproducts 7a and 8a were formed. Similar results were
obtained lowering the reaction temperature and increasing the
CO pressure (Table 1, entries 7-8). On the contrary, a complete
selectivity towards hydrosilylated compounds was observed
when the reaction was performed with 1 mol % of Rh4(CO)12
(Table 1, entry 9, note [e], 7a, 8a, 9a).
Finally, the silylcarbocyclisation of ethynylbenzylalcohol 1 with
dimethylphenylsilane 4a promoted by Rh+[(C7H8)(BPh4)]- (100°C,
30atm CO), afforded isochroman-3-one 5a with good
chemoselectivity (65%, Table 1 entry 11).
The silylcarbocyclization was then applied to hydrosilanes
having different stereoelectronic properties (Table 1, entries 12-
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15). The reactions were performed at 100°, under 50 atm CO,
for 4-6 hs with 0.2 mol% of rhodium species. As it is evident
from the results, the catalysts plays an important role in the
selectivity of the process (Table 1, entries 12,13), Rhsw being the
better choice. All methyleneisochroman-3-ones 5b-d were
obtained in good yields (not optimized) and the use of a very
hindered silane such as dimethyl(naphthalen-1-yl)silane 4c
seemed to promote the cyclisation process, in agreement with
our previous results on the silylcarbocyclisation of propargyl
alcohols6c.
The same chemoselectivity was detected when the reaction was
carried out with an increased amount of catalyst (Table 3, entry
2). In order to clarify if the observed results could be ascribed to
the steric hindrance of TMS group on alkyne 3, 2-(hex-1-yn-1-
yl)benzylalcohol 11 was reacted with dimethylphenylsilane 4a
under CO atmosphere. One more time the exclusive formation
of silylether 13b occurred (Table 3, entries 3, 4).
Table 2. TBAF-promoted aryl migration of (Z)-4-((dimethyl(aryl)silyl)
methylene)isochroman-3-ones 5a-d.
The reactions resulted totally stereoselective since only Z
isomers were formed. The configuration of the double bond of
the olefinic moiety was determined by analysis of the results
obtained with
a
NOESY (Nuclear Overhauser Effect
SpectroscopY) experiment (see fig. S42 in SI). As shown in
Figure 1, relevant NOE effects were detected between vinylic
proton Ha and aromatic Hb and between Hc and benzyl protons
Hd, thus indicating the exclusive formation of (Z)-isochroman-3-
one 5a.
Entry[a]
5
Ar
10
Yield[b]
1
2
3
4
a
b
c
d
Ph
a
b
c
d
76
82
68
81
4-MePh
1-Naptht
4-PhPh
[a] Reactions were performed at rt with 1mmol of methyleneisochroman-3-
ones and 5mmol of TBAF. [b] Yield of pure products.
Figure 1. Structure of isochroman-3-one 5a.
Finally, the reaction between alkyne 12 and [1,1'-biphenyl]-4-
yldimethylsilane 4d afforded 13c (Table 3, entries 5,6), thus
indicating that the cyclization process is clearly disfavored by the
presence of an internal triple bond, regardless of the structure of
the hydrosilane employed.
As far as the hydrogenated by-products 6 are concerned, it is
worth noting that this compounds can be useful building blocks
for the synthesis of polyfunctionalised molecules by means of
transformations involving the silyl group in the β position to the
carbonyl moiety11.
Table 3. Reactions of internal 2-ethynylbenzylalcohols 3, 11, 12 under
Once obtained, silylmethyleneisochroman-3-ones 5a-d were
submitted to desilylation by means of excess tetrabutyl
ammonium fluoride (1M in THF). According to our previous data6,
in the presence of TBAF, anionotropic migration of aryl group
from silicon to adjacent carbon atom occurred yielding
exclusively 4-(methylaryl)isochroman-3-ones 10a-d, (Table 2).
Prompted by these results, we decided to investigate the
extension of our silylcarbocyclisation/desilylation/aryl migration
sequence to internal 2-ethynylbenzyl alcohols, generated by a
simple Sonogashira reaction as depicted in Scheme 5.
silylcarbocyclization reaction conditions.
Entry[a]
R
4
Ar
13
Cat
(%)
t(h)
Conv.[b]
(%)
1
2
3
4
5
6
3
TMS
TMS
nBu
nBu
Ph
a
a
a
a
d
d
Ph
a
a
b
b
c
c
0.2
1
18
4
40
3
Ph
72 (52)
61
11
11
12
12
Ph
1
4
Ph
1
24
24
24
81 (68)
89
4-PhPh
4-PhPh
1
Scheme 5. Synthesis of 2-alkynylbenzyl alcohols 3, 11, 12.
Ph
2
91 (76)
[a] Reactions were performed with 3 mmol of alcohol, 3 mmol of silane 4, 3
mL of CH2Cl2 , at 100°C. [b] Conversions were determined by GC and 1H
NMR analysis.
First of all, 2-((trimethylsilyl)ethynylbenzyl alcohol 3 was tested
in the silylcarbocyclisation reaction operating under the same
experimental conditions optimised for terminal acetylene 1 (50
atm CO, 100°C, 0.2 mol %, Rhsw). After 18 h we observed a
partial conversion of the reagents (40%, Table 3, entry 1) and
the formation of silylether 13a as sole product.
A further proof of the synthesis of silylethers was obtained by
reacting 13b with TBAF. Indeed a quantitative desilylation to the
corresponding alcohol 11 was observed.
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However, the unexpected formation of silylethers under our
experimental conditions represents a quite interesting result
since transformation of alcohols into silylethers can be
considered one of the best methods for the protection of O-H
functional group. This reaction is generally performed in the
presence of hydrosilanes and alcohols but a transition metal
derived catalyst (Pt12, Pd13, Au14, Ru15, Cu16, Mn17; Ir18, Fe19,
Rh20) is necessary for silane alcoholysis to proceed at a
synthetically useful rate. In particular, with regard to the case of
rhodium promoted synthesis of silylethers, to our knowledge,
only a few examples are described in the literature20. On the
base of the obtained results, Rhsw can be considered a
promising catalyst for this reaction.
diazabicyclo[5.4.0]undec-7-ene, DBU) were put, under CO atmosphere,
in a 10 mL Pyrex Schlenk tube. This solution was introduced in the
autoclave, previously carried with Rh catalyst and placed under vacuum
(0.1 Torr), by a steel siphon. The reactor was pressurized with carbon
monoxide and the mixture was stirred for a selected time at a selected
temperature. After removal of excess CO (fume hood), the reaction
mixture was diluted with CH2Cl2, filtered on celite and the solvent was
removed under vacuum. The reagent conversion and the product
composition were determined by 1H-NMR spectroscopic analysis. All the
crude products were purified through column chromatography on silica
gel and characterized with 1H-NMR, 13C-NMR, FT-IR and GC-MS
techniques.
Silylcarbocyclization with dimethyl(phenyl)silane (4a) catalysed by
Rh4(CO)12 (0.1 mol%) with DBU (Table 1, entry 3). Following the
general procedure, 2.2 mg (0.003 mmol) of Rh4(CO)12, 396 mg (3.0
mmol) of (2-ethynylphenyl)methanol (1), 0.41 mL (3.0 mmol) of
dimethyl(phenyl)silane (4a), 45 μL (0.3 mmol) of DBU and 3 mL of
CH2Cl2 were put in the autoclave charged with 30 atm of CO. The
resulting mixture was stirred for 4 h at 70°C. The crude product was
purified through column chromatography (SiO2, CH2Cl2), obtaining 90 mg
(yield 10%) of (Z)-4-((dimethyl(phenyl)silyl) methylene)isochroman-3-one
Conclusions
In conclusion, we have successfully employed the
silylcarbocyclisation reaction in the preparation of functionalised
isochroman-3-ones. The reaction proceeds with good
chemoselectivity
towards
the
synthesis
of
methyleneisochroman-3-ones 5 only if 2-ethynylbenzyl alcohol 1
is employed and if the reaction is performed without a base. In
the presence of DBU the cyclisation is still favoured, but the
unsaturated isochroman-3-ones are readily hydrogenated,
generating the corresponding silylmethyl derivatives 6.
TBAF promoted aryl migration from silicon to the adjacent
carbon atom has been applied to silylmethyleneisochroman-3-
ones which yielded quantitatively the methylaryl derivatives 10.
On the contrary, when internal alkynes were tested under the
silylcarbocyclisation reaction conditions, no cyclisation occurred,
and silane alcoholysis selectively took place.
(5a)
and
600
mg
(yield
67%)
of
4-
((dimethyl(phenyl)silyl)methyl)isochroman-3-one (6a).
5a: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.66-7.64 (2H, m); 7.61-7.58
(1H, m); 7.39-7.32 (5H, m); 7.19-7.17 (1H, m); 7.03 (1H, s); 5.33 (2H, s);
0.58 (6H, s). 13C-NMR (75 MHz, CDCl3), δ (ppm): 160.82; 144.13;
139.58; 138.59; 133.79 (2C); 133.32; 130.17; 128.85; 128.73 (2C);
127.74 (2C); 124.25; 124.13; 69.20; - 2.18 (2C). FT-IR, max (cm-1): 3068;
2953; 1728; 1572; 1422; 1383; 1244; 1166. GC-MS, m/z (%): 294 (M+,
32); 281 (26); 279 (100); 217 (70); 173 (10); 137 (18); 115 (27); 75 (19).
6a: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.58-7.53 (2H, m); 7.41-7.38
(3H, m); 7.31-7.10 (4H, m); 5.42 (1H, d, J = 14.1 Hz); 5.23 (1H, d, J =
14.1 Hz); 3.69 (1H, t, J = 7.5 Hz); 1.61 (1H, dd, J = 14.8, 7.5 Hz); 1,39
(1H, dd, J = 14.8, 7.5 Hz); 0.39 (3H, s); 0.35 (3H, s). 13C-NMR (75 MHz,
CDCl3), δ (ppm): 173.64; 138.05; 136.37; 133.52 (2C); 131.42; 129.08;
128.48; 127.81 (2C); 126.94; 125.81; 124.66; 69.21; 41.97; 15.94; - 2.39;
- 2.55. FT-IR, max (cm-1): 2953; 1744; 1425; 1383; 1247; 1113. GC-MS,
m/z (%): 281 (M+ - CH3, 13); 209 (8); 147 (22); 129 (100); 128 (38); 111
(97); 110 (28); 84 (20); 71 (41); 55 (69).
Keywords: Isochromanone, cyclisation, carbon monoxide,
hydrosilane, silylether
Experimental Section
General remarks. Solvents were purified by conventional methods,
distilled and stored under argon. Noncommercial silanes 4b-d were
Silylcarbocyclization with dimethyl(phenyl)silane (4a) catalysed by
Rh4(CO)12 (0.1 mol%) without DBU (Table 1, entry 6). Following the
general procedure, 2.2 mg (0.003 mmol) of Rh4(CO)12, 396 mg (3.0
mmol) of (2-ethynylphenyl)methanol (1), 0.41 mL (3.0 mmol) of
dimethyl(phenyl)silane (4a) and 3 mL of CH2Cl2 were put in the autoclave
charged with 30 atm of CO. The resulting mixture was stirred for 2 h at
100°C. The crude product was purified through column chromatography
(SiO2, CH2Cl2), obtaining 371 mg (yield 42%) of (Z)-4-
((dimethyl(phenyl)silyl)methylene) isochroman-3-one (5a), 62 mg (yield
7%) of 4-((dimethyl(phenyl)silyl)methyl)isochroman-3-one (6a) and 161
prepared from the corresponding Grignard reagents according to the
22
method described by Hiyama and Fujita.21 Rh4(CO)12
and
Rh+[(C7H8)(BPh4)]-23 were prepared according to literature. All the other
chemicals were purchased from commercial sources and used as
received. 1H-NMR (300 MHz) and 13C-NMR (75 MHz) spectra were
recorded in CDCl3 solution with a Varian XL 300 spectrometer, with
CHCl3 as internal standard;  values are given in parts per million (ppm)
and coupling constants (J) in hertz. Mass spectra were obtained with a
Varian Saturn® Ion Trap 2000 mass spectrometer connected to a Varian
3800 gas chromatograph. FT-IR spectra were recorded with a Fourier
Transform Infrared Perkin-Elmer 1710 spectrophotometer, operating in
the range 4000-400 cm-1. Column chromatography was performed on
silica gel 60 (70-230 mesh). All products were identified and
characterized by spectroscopic and spectrometric data.
mg
(yield
20%)
of
a
mixture
(7a)
of
(E)-(2-(2-
(dimethyl(phenyl)silyl)vinyl)phenyl)methanol
and
(2-(1-
(dimethyl(phenyl)silyl)vinyl)phenyl)metha-nol (8a) in the molar ratio
65/35.
7a + 8a: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.63-7.18 (9.65H, m); 6.57
(0.65H, d, J = 19.0 Hz); 5.85 (0.35H, d, J = 3.2 Hz); 5.78 (0.35H, d, J =
3.2 Hz); 4.73 (1.3H, s); 4.34 (0.7H, s); 2.15 (1H, bs); 0.49 (3.9H, s); 0.42
(2.1H, s). GC-MS 7a, m/z (%): 253 (M+ - CH3, 3); 231 (2); 209 (2); 192
(53); 194 (15); 191 (8); 165 (2); 143 (1); 138 (7); 135 (100); 115 (13); 105
General procedure for silylcarbocyclizations of 2-ethynylbenzyl
alcohol 1. Silylcarbocyclization reactions were performed in a 25 mL
stainless steel autoclave fitted with a Teflon inner crucible and a
magnetic stirring bar. In
a
typical run, ethynylbenzyl alcohol 1,
1,8-
dimethyl(aryl)silane (1.0 eq.) and CH2Cl2 (and eventually
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(6); 76 (14); 75 (22); 74 (4). GC-MS 8a, m/z (%): 253 (M+ - CH3, 21); 190
5c: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.97-7.83 (4H, m); 7.56-7.44
(4H, m); 7.35-7.29 (2H, m); 7.19 (1H, s); 7.17-7.14 (1H, m); 5.28 (2H, s);
0.74 (6H, s).13C-NMR (75 MHz, CDCl3), δ (ppm): 165.84; 144.66; 138.17;
137.52; 136.31; 133.69; 133.52; 133.34; 130.23; 129.75; 129.25; 128.73;
128.70; 128.19; 125.57; 125.20; 125.17; 124.38; 124.14; 69.25; - 1.25
(2C). GC-MS, m/z (%): 344 (M+, 33); 329 (100); 285 (16); 217 (75); 173
(10); 145 (6); 115 (25); 75 (12).
6c: 1H-NMR (300 MHz, CDCl3), δ (ppm): 8.06-8.03 (1H, m); 7.89-7.86
(2H, m); 7.69-7.66 (1H, m); 7.51-7.43 (3H, m); 7.18-7.10 (3H, m); 6.94-
6.92 (1H, m); 5.37 (1H, d, J = 14.0 Hz); 5.16 (1H, d, J = 14.0 Hz); 3.68
(1H, t, J = 7.5 Hz); 1.79 (1H, dd, J = 15.0, 7.5 Hz); 1.62 (1H, dd, J = 15.0,
7.5 Hz); 0.57 (3H, s); 0.49 (3H, s). 13C-NMR (75 MHz, CDCl3), δ (ppm):
173.68; 136.73; 136.20; 135.98; 133.96; 133.38; 131.47; 130.13; 129.24;
128.37; 127.56; 126.94; 125.92; 125.89; 125.38; 125.10; 124.59; 69.30;
42.25; 16.57; - 0.59; - 1.15. FT-IR, max (cm-1): 2953; 1741; 1457; 1249;
1142. GC-MS, m/z (%): 316 (M+ - CH2O, 17); 283 (51); 241 (72) ; 185
(21); 149 (65); 127 (18); 115 (100); 103 (13); 75 (42).
7c + 8c: 1H-NMR (300 MHz, CDCl3), δ (ppm): 8.24-8.20 (0.85H, m);
8.16-8.04 (0.30H, m); 7.93-7.80 (3.70H, m); 7.73-7.70 (0.30H, m); 7.63-
7.60 (0.85H, m); 7.53-7.50 (3H, m); 7.39-7.26 (2.55H, m); 7.19-7.11
(0.30H, m); 6.75 (0.85H, d, J = 19.0 Hz); 5.91 (0.15H, d, J = 3.3 Hz); 5.83
(0.15H, d, J = 3.3 Hz); 4.70 (1.70H, s); 4.46 (0.30H, s); 1.68 (0.85H, s);
1.30 (0.15H, s); 0.66 (5.1H, s); 0.58 (0.9H, s). GC-MS 7c, m/z (%): 318
(M+, 7); 301 (M+ - OH, 12); 243 (54); 188 (14); 185 (100); 141 (16); 115
(27); 75 (63); 47 (6). GC-MS 8c, m/z (%): 303 (M+ - CH3, 47); 283 (8);
187 (42); 185 (81); 141 (12); 115 (46); 75 (100); 43 (8).
(43); 136 (32); 135 (100); 115 (50); 107 (11); 75 (46).
Silylcarbocyclization with dimethyl(phenyl)silane (4a) catalysed by
Rh4(CO)12 (1 mol%) without DBU (Table 1, entry 9).
Following the general procedure, 22 mg (0.03 mmol) of Rh4(CO)12, 396
mg (3.0 mmol) of (2-ethynylphenyl)methanol (1), 0.41 mL (3.0 mmol) of
dimethyl(phenyl)silane (4a) and 3 mL of CH2Cl2 were put in the autoclave
charged with 50 atm of CO. The mixture was stirred for 24 h at 30°C. The
composition of crude product was determined by 1H-NMR and GC-MS
analysis,
resulting
in
a
mixture
of
(7a),
and
(E)-(2-(2-
(2-(1-(di-
(Z)-(2-(2-
(dimethyl(phenyl)silyl)vinyl)phenyl)methanol
methyl(phenyl)silyl)vinyl)phenyl)metha-nol
(8a)
(dimethyl(phenyl)silyl)vinyl)phenyl)methanol (9a) in the molar ratio
48/34/18.
7a + 8a + 9a: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.63-7.13 (9.66H, m);
6.60 (0.48H, d, J = 19.0 Hz); 6.18 (0.18H, d, J = 14.6 Hz); 5.85 (0.34H, d,
J = 3.2 Hz); 5.78 (0.34H, d, J = 3.2 Hz); 4.80 (0.96H, s); 4.62 (0.36H, s);
4.38 (0.68H, s); 1.82 (0.82H, bs); 1.30 (0.18H, bs); 0.49 (2.88H, s); 0.42
(2.04H, s); 0.37 (1.08H, s). GC-MS 9a, m/z (%): 268 (M+, 41); 239 (16);
223 (27); 192 (26); 177 (73); 149 (88); 115 (100); 91 (47); 75 (53).
Silylcarbocyclization with dimethyl(p-tolyl)silane (4b) (Table 1, entry
13). Following the general procedure, 3.4 mg (0.006 mmol) of
Rh+[(C7H8)(BPh4)]-, 396 mg (3.0 mmol) of (2-ethynylphenyl) methanol (1),
451 mg (3.0 mmol) of dimethyl(p-tolyl)silane (4b) and 3 mL of CH2Cl2
were put in the autoclave charged with 50 atm of CO. The resulting
mixture was stirred for 4 h at 100°C. The crude product was purified
through column chromatography (SiO2, CH2Cl2), obtaining 463 mg (yield
50%) of (Z)-4-((dimethyl(p-tolyl)silyl)methylene)isochroman-3-one (5b)
Silylcarbocyclization with [1,1'-biphenyl]-4-yldimethylsilane (4d)
(Table 1, entry 15). Following the general procedure, 3.4 mg (0.006
mmol) of Rh+[(C7H8)(BPh4)]-, 396 mg (3.0 mmol) of (2-ethynylphenyl)
methanol (1), 638 mg (3.0 mmol) of [1,1'-biphenyl]-4-yldimethylsilane
(4d) and 3 mL of CH2Cl2 were put in the autoclave charged with 50 atm
of CO. The resulting mixture was stirred for 6 h at 100°C. The crude
product was purified through column chromatography (SiO2, CH2Cl2),
obtaining 678 mg (yield 61%) of (Z)-4-(([1,1'-biphenyl]-4-yldimethyl
silyl)methylene)isochroman-3-one (5d), 45 mg (yield 4%) of 4-(([1,1'-
biphenyl]-4-yldimethylsilyl)methyl)isochroman-3-one (6d) and 72 mg
(yield 7%) of (E)-(2-(2-([1,1'-biphenyl]-4-yldimethylsilyl)vinyl)phenyl)
methanol (7d).
5d: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.84 (2H, d, J = 7.8 Hz); 7.72-
7.64 (5H, m); 7.54-7.49 (2H, m); 7.44-7.37 (3H, m); 7.20-7.17 (1H, m);
7.15 (1H, s); 5.35 (2H, s); 0.72 (6H, s). 13C-NMR (75 MHz, CDCl3), δ
(ppm): 165.91; 143.92; 141.56; 141.05; 138.58; 138.22; 134.32 (2C);
133.19; 130.13; 128.73 (2C); 128.68 (2C); 127.27; 127.09 (2C); 126.46
(2C); 124.23; 124.12; 69.19; -2.04 (2C). GC-MS, m/z (%): 370 (M+, 47);
355 (100); 217 (47); 173 (11); 143 (11); 115 (31); 75 (12).
6d: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.63-7.60 (6H, m); 7.49-7.44
(2H, m); 7.39-7.33 (1H, m); 7.30-7.24 (2H, m); 7.21-7.18 (1H, m); 7.14-
7.11 (1H, m); 5.41 (1H, d, J = 13.9 Hz); 5.23 (1H, d, J = 13.9 Hz); 3.70
(1H, t, J = 7.5Hz); 1.62 (1H, dd, J = 15.0, 7.5 Hz); 1.41 (1H, dd, J = 15.0,
7.5 Hz); 0.40 (3H, s); 0.36 (3H, s). 13C-NMR (75 MHz, CDCl3), δ (ppm):
173.68; 141.86; 140.88; 136.86; 136.43; 134.11 (2C); 131.49; 128.74
(2C); 128.57; 127.40; 127.08 (2C); 127.02; 126.57 (2C); 125.90; 124.74;
69.30; 42.06; 16.04; - 2.22; - 2.43. FT-IR, max (cm-1): 2951; 1742; 1459;
1247; 1165. GC-MS, m/z (%): 357 (M+ - CH3, 100); 219 (35); 167 (6); 115
(7).
and 170 mg (yield 20%) of
tolyl)silyl)vinyl)phenyl) methanol
a
mixture of (E)-(2-(2-(dimethyl(p-
(7b) and (2-(1-(dimethyl(p-
tolyl)silyl)vinyl)phenyl)methanol (8b) in the molar ratio 66/34.
5b: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.48-7.43 (3H, m); 7.25-7.21
(2H, m); 7.13-7.03 (3H, m); 6.92 (1H, s); 5.19 (2H, s); 2.25 (3H, s); 0.46
(6H, s). 13C-NMR (75 MHz, CDCl3), δ (ppm): 165.86; 144.39; 138.66;
138.45; 135.78; 133.83 (2C); 133.36; 130.14; 128.68; 128.63; 128.56
(2C); 124.19; 124.08; 69.14; 21.42; - 2.09 (2C). FT-IR, max (cm-1): 3010;
2953; 1730; 1602; 1460; 1245; 1169. GC-MS, m/z (%): 308 (M+, 6); 294
(16); 293 (68); 249 (9); 218 (19); 217 (100); 151 (11); 115 (20); 75 (10).
7b + 8b: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.56-7.09 (8.66H, m); 6.52
(0.66H, d, J = 19.0 Hz); 5.75 (0.34H, d, J = 3.3 Hz); 5.67 (0.34H, d, J =
3.3 Hz); 4.66 (1.32H, bs); 4.29 (0.68H, bs); 2.32 (1.98H, s); 2.30 (1.02H,
s); 2.17 (0.66H, bs); 1.50 (0.34H, bs); 0.42 (3.96H, s); 0.35 (2.04H, s).
GC-MS 7b, m/z (%): 282 (M+, 0.2); 267 (M+ - CH3, 0.6); 253 (0.8); 206
(50); 149 (100); 115 (10); 75 (19). GC-MS 8b, m/z (%): 267 (M+ - CH3,
14); 190 (28); 151 (45); 149 (100); 115 (29); 75 (56).
Silylcarbocyclization with dimethyl(naphthalen-1-yl)silane (4c)
(Table 1, entry 14). Following the general procedure, 3.4 mg (0.006
mmol) of Rh+[(C7H8)(BPh4)]-, 396 mg (3.0 mmol) of (2-ethynylphenyl)
methanol (1), 560 mg (3.0 mmol) of dimethyl(naphthalen-1-yl)silane (4c)
and 3 mL of CH2Cl2 were put in the autoclave charged with 50 atm of
CO. The resulting mixture was stirred for 4 h at 100°C. The crude product
was purified through column chromatography (SiO2, CH2Cl2), obtaining
620
mg
(yield
60%)
of
(Z)-4-((dimethyl(naphthalen-1-yl)
silyl)methylene)isochroman-3-one (5c), 42 mg (yield 4%) of 4-
((dimethyl(naphthalen-1-yl)silyl)methyl)isochroman-3-one (6c) and 76 mg
7d: 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.71-7.62 (8H, m); 7.50-7.45
(2H, m); 7.41-7.29 (4H, m); 6.61 (1H, d, J = 18.9 Hz); 4.80 (2H, d, J = 5.4
Hz); 1.72 (1H, t, J = 5.4 Hz); 0.51 (6H, s). 13C-NMR (75 MHz, CDCl3), δ
(ppm): 142.00; 141.84; 141.01; 137.46; 137.21; 137.17; 134.37 (2C);
130.49; 128.74 (2C); 128.19; 128.15; 128.10; 127.36; 127.13 (2C);
(yield 8%) of
a
mixture of of (E)-(2-(2-(dimethyl(naphthalen-1-
yl)silyl)vinyl) phenyl)methanol (7c) and (2-(1-(dimethyl(naphthalen-1-
yl)silyl)vinyl)phenyl)methanol (8c) in the molar ratio 85/15.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700455
European Journal of Organic Chemistry
FULL PAPER
126.57 (2C); 125.96; 63.18; - 2.45 (2C). FT-IR, max (cm-1): 3351; 3059;
1596; 1482; 1250; 1112. GC-MS, m/z (%): 268 (M+ - C6H5, 69); 211
(100); 165 (12); 115 (15); 75 (35).
14.1, 4.8 Hz); 3.53 (1H, dd, J = 14.1, 8.8 Hz). 13C-NMR (75 MHz, CDCl3),
δ
(ppm): 172.47; 133.63; 133.57; 132.88; 131.46; 130.79; 128.72;
128.11; 127.62; 127.56; 127.17 (2C); 126.18; 125.56; 124.97; 124.29;
123.08; 69.49; 46.54; 34.10. FT-IR, max (cm-1): 2923; 1737; 1385; 1191.
GC-MS, m/z (%): 288 (M+, 18); 243 (9); 141 (100); 115 (22); 50 (5).
General procedure for TBAF-promoted aryl migration of (Z)-4-
((dimethyl(aryl)silyl)methylene)isoch-roman-3-ones 5a-d. In a typical
run, 1.0 M in THF tetrabutylammonium fluoride and distilled THF were
mixed together in a a 50 mL two-necked round bottom flask, equipped
with dropping funnel and magnetic stirring bar, then a solution of 4-
((dimethyl-arylsilyl)methylene)isochroman-3-one 5 in distilled THF was
dropped. The mixture was left under stirring for 30 minutes at room
temperature, then it was hydrolyzed with water and extracted with CH2Cl2.
The combined organic phases were washed with brine, dried over
anhydrous Na2SO4 and the solvent was removed under vacuum. All the
crude products were purified through column chromatography on silica
gel and characterized with 1H-NMR, 13C-NMR, FT-IR and GC-MS
techniques.
4-([1,1'-biphenyl]-4-ylmethyl)isochroman-3-one (10d) (Table 2, entry
4). Following the general procedure, a solution of 678 mg (1.8 mmol) of
(Z)-4-(([1,1'-biphenyl]-4-yldimethylsilyl) methylene)isochroman-3-one (5d)
in 8 mL of THF was dropped in a mixture of 5.0 mL (5.0 mmol) of 1.0 M
in THF tetrabutylammonium fluoride and 10 mL of THF. The crude
product was purified through column chromatography (SiO2, CH2Cl2),
obtaining 458 mg (yield 81%) of 4-([1,1'-biphenyl]-4-ylmethyl)isochroman-
3-one (10d) as colourless oil. 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.61-
7.58 (2H, m); 7.50-7.42 (4H, m); 7.38-7.26 (3H, m); 7.15-7.03 (4H, m);
5.12 (1H, d, J = 14.0 Hz); 4.84 (1H, d, J = 14.0 Hz); 4.04 (1H, t, J =6.6
Hz); 3.35 (2H, d, J = 6.6 Hz). 13C-NMR (75 MHz, CDCl3), δ (ppm):
172.32; 140.37; 139.60; 136.02; 133.36; 131.14; 129.56 (2C); 128.66
(2C); 128.35; 127.24; 127.20; 127.13; 126.89 (2C); 126.79 (2C); 124.18;
69.55; 47.11; 37.75. FT-IR, max (cm-1): 2923; 1741; 1385; 1194. GC-MS,
m/z (%): 314 (M+, 6); 269 (3); 253 (1); 167 (100); 152 (3); 115 (2); 91 (2);
63 (1).
4-benzylisochroman-3-one (10a)5 (Table 2, entry 1). Following the
general procedure,
a solution of 490 mg (1.7 mmol) of (Z)-4-
((dimethyl(phenyl)silyl)methylene) isochroman-3-one (5a) in 7 mL of THF
was dropped in a mixture of 5.0 mL (5.0 mmol) of 1.0 M in THF
tetrabutylammonium fluoride and 10 mL of THF. The crude product was
purified through column chromatography (SiO2, CH2Cl2), obtaining 308
mg (yield 76%) of 4-benzylisochroman-3-one (10a) as colourless oil, with
spectroscopic constants in agreement with those reported in the
literature5. 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.31-7.18 (5H, m); 7.14-
7.10 (1H, m); 7.01-6.96 (3H, m); 5.09 (1H, d, J = 14.2 Hz); 4.75 (1H, d, J
= 14.2 Hz); 4.01 (1H, t, J = 6.0 Hz); 3.30 (2H, d, J = 6.0 Hz). 13C-NMR
(75 MHz, CDCl3), δ (ppm): 172.36; 136.95; 133.44; 131.19; 129.19 (2C);
128.34 (3C); 127.26; 127.23; 126.90; 124.15; 69.56; 47.27; 38.35. FT-IR,
General procedure for silylcarbocyclization attempts of 2-
alkynylbenzyl alcohols 3, 11, 12. Reactions were performed in a 25 mL
stainless steel autoclave fitted with a Teflon inner crucible and a
magnetic stirring bar. In
a
typical run, alkynylbenzyl alcohol,
dimethyl(aryl)silane (1.0 eq.) and CH2Cl2 were put, under CO
atmosphere, in a 10 mL Schlenk tube. This solution was introduced in the
autoclave, previously carried with Rh+[(C7H8)(BPh4)]- and placed under
vacuum (0.1 Torr), by a steel siphon. The reactor was pressurized with
carbon monoxide (50 atm) and the mixture was stirred for a selected time
at 100 °C. After removal of excess CO (fume hood), the reaction mixture
was diluted with CH2Cl2, filtered on celite and the solvent was removed
under vacuum. The reagent conversion and the product composition
were deter-mined by 1H-NMR spectroscopic analysis. All crude products
were purified through column chromatography on silica gel and
characterized with 1H-NMR, 13C-NMR, FT-IR and GC-MS techniques.

max (cm-1): 2933; 1741; 1425; 1388; 1244; 1193; 1048.
4-(4-methylbenzyl)isochroman-3-one (10b) (Table 2, entry 2).
Following the general procedure, a solution of 463 mg (1.50 mmol) of (Z)-
4-((dimethyl(p-tolyl)silyl)methylene)isochro-man-3-one (5b) in 5 mL of
THF was dropped in a mixture of 5.0 mL (5.0 mmol) of 1.0 M in THF
tetrabutylammonium fluoride and 10 mL of THF. The crude product was
purified through column chromatography (SiO2, CH2Cl2), obtaining 310
mg (yield 82%) of 4-(4-methylbenzyl)isochroman-3-one (10b) as
colourless oil. 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.30-7.24 (2H, m);
7.12-7.07 (1H, m); 7.03-6.97 (3H, m); 6.85 (2H, d, J = 7.9 Hz); 5.07 (1H,
d, J = 14.4 Hz); 4.74 (1H, d, J = 14.4 Hz); 3.97 (1H, t, J = 6.3 Hz); 3.24
(2H, d, J = 6.3 Hz); 2.30 (3H, s). 13C-NMR (75 MHz, CDCl3), δ (ppm):
172.48; 136.45; 133.73; 133.52; 131.14; 129.01 (2C); 128.99 (2C);
128.29; 127.22; 127.17; 124.11; 69.56; 47.35; 38.00; 20.99. FT-IR, max
(cm-1): 2920; 1742; 1390; 1189. GC-MS, m/z (%): 252 (M+, 7); 207 (10);
160 (12); 105 (100); 77 (9).
((2-(((dimethyl(phenyl)silyl)oxy)methyl)phenyl)ethynyl)trimethylsilane
(13a) (Table 3, entry 2). Following the general procedure, 17 mg (0.03
mmol) of Rh+[(C7H8)(BPh4)]-, 614 mg (3.0 mmol) of (2-((trimethylsilyl)
ethynyl)phenyl)methanol
(3),
0.41
mL
(3.0
mmol)
of
dimethyl(phenyl)silane (4a) and 3 mL of CH2Cl2 were put in the autoclave.
The resulting mixture was stirred for 4 h. The crude product was purified
through column chromatography (SiO2, CH2Cl2), obtaining 528 mg (yield
52%)
of
((2-
(((dimethyl(phenyl)silyl)oxy)methyl)phenyl)ethynyl)trimethylsilane (13a).
1H-NMR (300 MHz, CDCl3), δ (ppm): 7.66-7.63 (2H, m); 7.60-7.55 (1H,
m); 7.44-7.33 (5H, m); 7.20 (1H, td, J = 7.5, 0.7 Hz); 4.90 (2H, s); 0.46
(6H, s); 0.24 (9H, s). 13C-NMR (75 MHz, CDCl3), δ (ppm): 143.02;
137.56; 133.44 (2C); 131.74; 129.62; 128.68; 127.86 (2C); 126.49;
126.06; 120.09; 102.41; 99.37; 63.10; - 0.05 (3C); - 1.78 (2C). GC-MS,
m/z (%): 338 (M+, 6); 323 (M+ - CH3, 15); 265 (100); 233 (53); 193 (15);
149 (19); 135 (45); 128 (8); 105 (10); 73 (32); 45 (23).
4-(naphthalen-1-ylmethyl)isochroman-3-one (10c) (Table 2, entry 3).
Following the general procedure, a solution of 620 mg (1.8 mmol) of (Z)-
4-((dimethyl(naphthalen-1-yl)silyl)methylene) isochroman-3-one (5c) in 8
mL of THF was dropped in a mixture of 5.0 mL (5.0 mmol) of 1.0 M in
THF tetrabutylammonium fluoride and 10 mL of THF. The crude product
was purified through column chromatography (SiO2, CH2Cl2), obtaining
353 mg (yield 68%) of 4-(naphthalen-1-ylmethyl)isochroman-3-one (10c)
as colourless oil. 1H-NMR (300 MHz, CDCl3), δ (ppm): 8.05-7.99 (1H, m);
7.89-7.86 (1H, m); 7.76 (1H, d, J = 8.4 Hz); 7.54-7.46 (2H, m); 7.31-7.22
(2H, m); 7.13 (2H, t, J = 7.1 Hz); 7.00 (1H, d, J = 7.1 Hz); 6.68 (1H, d, J =
7.1 Hz); 5.16 (2H, s); 4.13 (1H, dd, J = 8.8, 4.8 Hz); 3.89 (1H, dd, J =
((2-(hex-1-yn-1-yl)benzyl)oxy)dimethyl(phenyl)silane (13b) (Table 3,
entry 4). Following the general procedure, 23 mg (0.04 mmol) of
Rh+[(C7H8)(BPh4)]-, 754 mg (4.0 mmol) of (2-(hex-1-yn-1-yl)
phenyl)methanol (11), 0.55 mL (4.0 mmol) of dimethyl(phenyl)silane (4a)
and 3 mL of CH2Cl2 were put in the autoclave. The resulting mixture was
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201700455
European Journal of Organic Chemistry
FULL PAPER
Zhou, Y. Tao, Yachun; Yu, Qiang; Zhou, Bin; Liu, Yuchao 2015, CN
105061375.
stirred for 24 h. The crude product was purified through column
chromatography (SiO2, CH2Cl2), obtaining 877 mg (yield 68%) of ((2-
(hex-1-yn-1-yl)benzyl)oxy)dimethyl(phenyl)silane (13b). 1H-NMR (300
MHz, CDCl3), δ (ppm): 7.66-7.63 (2H, m); 7.57-7.54 (2H, m); 7.42-7.28
(4H, m); 7.21-7.16 (1H, m); 4.88 (2H, s); 2.41 (2H, t, J = 6.9 Hz); 1.61-
1.41 (4H, m); 0.94 (3H, t, J = 6.0 Hz); 0.45 (6H, s). 13C-NMR (75 MHz,
CDCl3), δ (ppm): 142.45; 137.88; 133.64 (2C); 131.73; 129.77; 128.01
(2C); 127.83; 126.66; 126.15; 121.25; 95.53; 78.13; 63.44; 30.96; 22.12;
19.37; 13.81; - 1.54 (2C). FT-IR, max (cm-1): 1422; 1251; 1072; 1115.
GC-MS, m/z (%): 322 (M+, 7); 307 (M+ - CH3, 16); 280 (31); 235 (17); 205
(49); 169 (24); 135 (100); 115 (28); 91 (18); 75 (32).
[2]
[3]
a) R. J. Spangler, J. Ho Kim, Synthesis 1973, 107-108; b) R. J.
Spangler, B. G. Beckmann, J. Ho Kim, J. Org. Chem. 1977, 42, 2989-
2995; G. J. Brink; I. W. C. E. Arends, R. A. Sheldon, Chem. Rev. 2004,
104, 4105-4123; M. Y. Rios, E. Salazar, H. F. Olivo, J. Mol. Cat. 2008,
54, 61-66.
a) T. Kametani, Y. Enomoto, K. Takahashi, K. Fukumoto, J. Chem. Soc.
Perkin 1 1979, 2836-2838; b) K. Shishido, E. Shitaka, K. Fukumoto, T.
Kametani, J. Am. Chem. Soc. 1985, 107, 5810-5812; c) K. Shishido, K.
Hiroya, K.Fukumoto, T. Kametani, Tetrahedron Lett. 1986, 27, 971-974;
d) K. Shishido, E. Shitara, H. Komatsu, K. Hiroya, K. Fukumoto, T.
Kametani, J. Org. Chem, 1986, 51, 3007-3011; e) K. Shishido, H.
Komatsu, K. Fukumoto, Heterocycles 1987, 26, 2361-2364; f) K.
Shishido, H. Komatsu, K. Fukumoto, T. Kametani, Hetrocycles 1989, 28,
43-46.
[1,1'-biphenyl]-4-yldimethyl((2-(phenylethynyl)benzyl)oxy)silane
(13c) (Table 3, entry 6). Following the general procedure, 21 mg (0.036
mmol) of Rh+[(C7H8)(BPh4)]-, 375 mg (1.8 mmol) of (2-(phenylethynyl)
phenyl)methanol (12), 383 mg (1.8 mmol) of [1,1'-biphenyl]-4-
yldimethylsilane (4d) and 3 mL of CH2Cl2 were put in the autoclave. The
resulting mixture was stirred for 24 h. The crude product was purified
through column chromatography (SiO2, CH2Cl2), obtaining 573 mg (yield
76%) of [1,1'-biphenyl]-4-yldimethyl((2-(phenylethynyl)benzyl)oxy)si-lane
(13c). 1H-NMR (300 MHz, CDCl3), δ (ppm): 7.77-7.75 (1H, m); 7.68-7.62
(7H, m); 7.52-7.44 (5H, m); 7.43-7.28 (5H, m); 5.05 (2H, s); 0.53 (6H, s).
13C-NMR (75 MHz, CDCl3), δ (ppm): 142.41; 142.31; 140.90; 136.17;
134.00; 133.48; 131.65; 131.40 (2C); 128.83; 128.71 (2C); 128.50;
128.28; 128.23; 127.40; 127.10 (2C); 126.73; 126.57 (2C); 126.42;
123.15; 120.34; 94.14; 86.81; 63.28; - 1.62 (2C). FT-IR, max (cm-1):
1440; 1253; 1069; 1116. GC-MS, m/z (%): 418 (M+, 49); 344 (100); 264
(13); 191 (10); 75 (10).
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Synthesis of precursors (1, 3, 11, 12) and copies of the 1H-NMR and 13C-
NMR spectra of all product synthesized.
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A rhodium promoted
Silylcarbocyclisation, Isochromanone
silylcarbocyclization reaction between
2-alkynylbenzyl alcohols and
hydrosilanes under CO atmosphere is
reported. Different products can be
obtained depending on the
Gianluigi Albano, Martina Morelli, Laura
Antonella Aronica*
Author(s), Corresponding Author(s)*
Page No. – Page No.
experimental conditions and on the
nature of the alkynes. When terminal
acetylenes are reacted under CO
pressure and without base,
(dimethylarylsilyl)methylene
isochroman-3-ones are obtained in
good yields.
A New Synthesis of Functionalised 3-
Isochromanones via
Silylcarbocyclisation-Desilylation
reactions
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