Highly stereoselective addition of stannylcuprates to alkynones

Article abstract of DOI:10.1021/jo0259008

The addition of stannylcuprate reagents such as (Bu₃Sn)(PhS)CuLi to alkynones has been found to proceed in high yield and with excellent stereoselectivity for the Z isomer of the product (>95%). The behavior of the stannylcuprates is thus very different from that of their "carbocuprate" counterparts such as Me₂CuLi or Me₂Cu(CN)Li₂ which are nonstereoselective. Furthermore, in contrast to the reactions of (R₃Sn)(PhS)CuLi with the corresponding alkynoates, the presence of a proton source in the reaction medium has no effect on the stereoselectivity of the reaction of alkynones.

Full text of DOI:10.1021/jo0259008

High ly Ster eoselective Ad d ition of Sta n n ylcu p r a tes to Alk yn on es
Thomas E. Nielsen, Maria A. Cubillo de Dios, and David Tanner*
Department of Chemistry, Technical University of Denmark, Building 201, Kemitorvet,
DK-2800 Kgs. Lyngby, Denmark
dt@kemi.dtu.dk
Received May 3, 2002
The addition of stannylcuprate reagents such as (Bu3Sn)(PhS)CuLi to alkynones has been found
to proceed in high yield and with excellent stereoselectivity for the Z isomer of the product (>95%).
The behavior of the stannylcuprates is thus very different from that of their ”carbocuprate”
counterparts such as Me2CuLi or Me2Cu(CN)Li2 which are nonstereoselective. Furthermore, in
contrast to the reactions of (R3Sn)(PhS)CuLi with the corresponding alkynoates, the presence of a
proton source in the reaction medium has no effect on the stereoselectivity of the reaction of
alkynones.
SCHEME 1
In tr od u ction
Organocopper reagents provide one of the most reliable
and versatile tools for carbon-carbon or carbon-het-
eroatom bond formation, either by substitution, conjugate
addition, or carbocupration reactions.1 As is often the case
with organometallics, detailed mechanistic insight that
is essential to the development of even more efficient
reagents can be gleaned only with difficulty and not
without some controversy.2 However, recent theoretical,
kinetic, and spectroscopic studies have gone some way
to improving the ”black box” reputation of organocopper
chemistry.3 An important mechanistic study by Ullenius
and co-workers4 recently highlighted the opportunities
and difficulties associated with addition of organocu-
prates to alkynoates5 and alkynones. Our interest in
stereoselective stannylcupration of the latter substrates
(Scheme 1) was awakened during the course of a total
synthesis program,6 and was further prompted by the
pioneering work of Piers7 on the addition of stannylcu-
prates to acetylenic esters. In the present paper we
describe unusually high stereoselectivity (>95%) in the
addition of stannylcuprates to alkynones 1.
SCHEME 2
Alkynone 1d was chosen for the initial studies, using
three different stannylcuprate reagents under the condi-
tions shown in Table 1. We were initially most interested
to investigate if the Z/E ratio of the products could be
affected by variation of the reaction temperature and the
presence (or absence) of a proton source (methanol) in
the reaction medium.7 In contrast to the corresponding
alkynoates7,9 and contrary to previous studies10 involving
”carbocuprates” the alkynones delivered exclusively the
Z isomer of the product under all reaction conditions
tested. The E isomer, if present at all, could not be
Resu lts a n d Discu ssion
The alkynones8 1a -k chosen for the present study
were prepared by two simple and complementary meth-
ods: (A) addition of lithium acetylides to Weinreb amides,
and (B) Sonogashira coupling of terminal alkynes with
acid chlorides (Scheme 2 and Experimental Section).
1
detected in the high-field H NMR spectra of the crude
(1) Lipshutz, B. H.; Sengupta, S. Org. React. 1992, 41, 135.
(2) Nakamura, E.; Mori, S. Angew. Chem., Int. Ed. 2000, 39, 3750.
(3) Woodward, S. Chem. Soc. Rev. 2000, 9, 393.
(4) Nilsson, K.; Andersson, T.; Ullenius, C.; Gerold, A.; Krause, N.
Chem. Eur. J . 1998, 4, 2051.
(5) For a recent example, see: Williams, D. R.; Fromhold, M. G.;
Earley, J . D. Org. Lett. 2001, 3, 2721.
products. The stereochemistry of the product 2d was
determined11 by NMR spectroscopy, where the coupling
constant from the vinyl proton to tin, J (Sn-H), was found
to be 110 Hz. As indicated in footnote d in Table 1,
trapping12 of the presumed organocopper intermediate
(6) Tanner, D.; Tedenborg, L.; Somfai, P. Acta Chem. Scand. 1997,
51, 1217.
(7) Piers, E.; Morton, H. E. J . Org. Chem. 1980, 45, 4263.
(8) For leading references, see: Kel’in, A.; Gevorgyan, V. J . Org.
Chem. 2002, 67, 95.
(9) Piers, E.; Chong, J . M.; Morton, H. E. Tetrahedron 1989, 45, 363.
(10) For leading references, see ref 4.
(11) For typical J (Sn-H) values, see refs 9 and 14.
10.1021/jo0259008 CCC: $22.00 © 2002 American Chemical Society
Published on Web 09/20/2002
J . Org. Chem. 2002, 67, 7309-7313
7309

Nielsen et al.
TABLE 1. Sta n n ylcu p r a tion of Alk yn on es I
additions to acetylenic ketones. Our results obviously
have mechanistic implications worthy of further study,
and we are currently investigating this reaction by a
combination of experimental, spectroscopic, and theoreti-
cal techniques. Results will be published in due course.
Con clu sion s
We have demonstrated that stannylcuprates add to
alkynones in high yield and with unprecedentedly high
stereoselectivity (>95%), the Z isomer being the exclusive
product. In our experience, the present method generally
gives higher yields than can be obtained by alternative
routes15 and gives convenient access to functionalized
trisubstituted alkenes which are useful building blocks
for further synthesis (e.g. via cross-coupling reactions).16
A solution to the problem of obtaining the corresponding
E isomers is given elsewhere.17
MeOH
temp
(°C)
product yield
entry
stannylcuprate
(+/-)a
of 2d (%)b,c
1
2d
3
4
5
6
7
8
(Bu3Sn)(PhS)CuLi
(Bu3Sn)(PhS)CuLi
(Bu3Sn)(PhS)CuLi
(Bu3Sn)(PhS)CuLi
(Bu3Sn)(CN)CuLi
(Bu3Sn)(CN)CuLi
Bu3SnCu‚Me2S
-
-
+
+
-
+
-
+
-78
-78
-78
-20
-78
-78
-78
-78
>95
>95
75
58
>95
77
44
36
Bu3SnCu‚Me2S
Exp er im en ta l Section
a
(+) indicates that MeOH (1.7 equiv) and alkynone 1d were
dissolved in the same THF solution and added to the stannylcu-
prate, and (-) indicates that alkynone 1d was added to the
1
Gen er a l Meth od s. H (300 MHz) and 13C (75 MHz) NMR,
and 1H (500 MHz) and 13C (125 MHz) NMR spectra were
recorded by using CDCl3 as the solvent, and signal positions
(δ values) were measured relative to the signals for CHCl3
(7.27) and CDCl3 (77.0), respectively. Tin-hydrogen coupling
constants, J (Sn-H), are given as the average of the 117Sn and
119Sn values. IR spectra were obtained for thin films on AgCl
plates, and only the strongest/structurally most important
peaks (νmax/cm-1) are listed. Microanalyses were performed by
the Microanalysis Laboratory, Department of Physical Chem-
istry, University of Vienna, Austria. HRMS was performed at
the Department of Chemistry, University of Copenhagen,
Denmark. Molecular mass determinations (high-resolution
mass spectrometry) for substances containing R3Sn (Bu3Sn or
Me3Sn) groups are based on 120Sn and typically made on the
[M - R]+, unless otherwise stated. All compounds on which
b
stannylcuprate in the absence of methanol. Isolated yield after
flash column chromatography. c None of the E isomer 3d could
d
be detected. When TLC indicated complete conversion of the
substrate, MeI (10 equiv) was added to the mixture, followed by
stirring for 1 h at -78 °C to afford none of the methylated product.
by electrophiles other than a proton was unfortunately
not possible.
On the basis of these encouraging results, we per-
formed some further screening of stannylcuprates
(Table 2).
Again, exclusive Z-selectivity was observed, with the
(Bu3Sn)(PhS)CuLi reagent13 generally providing the high-
est yields. THF was much superior to diethyl ether as
solvent (entry 2) and it is interesting to note that one of
the cuprates survived in the presence of 10 equiv of water
(entry 5).
The (Bu3Sn)(PhS)CuLi reagent was then selected for
the screening of acetylenic ketones summarized in Table
3. With the exception of entry 2, isolated yields were
uniformly excellent and the Z isomers were the exclusive
products which could be purified easily and with minimal
decomposition (protodestannylation) by conventional flash
chromatography. The configuration of the products was
determined by 1H NMR spectroscopy, where the coupling
constants of the vinyl proton to tin, J (Sn-H), of products
2a -k were measured to be within the range of 101-114
Hz, and NOE measurements (Figure 1).
1
HRMS were performed exhibited clean H proton NMR spectra
and showed one spot on TLC analysis. TLC analyses were
performed on Merck aluminum-backed F254 silica gel plates,
using UV light, and a solution of 5-10% phosphomolybdic acid
in ethanol, for visualization. All chromatography was per-
formed with use of Merck silica gel (40-63 µm). All solvents
were distilled prior to use. THF and diethyl ether were distilled
under nitrogen from Na-benzophenone. Diisopropylamine was
dried over calcium hydride and distilled under nitrogen.
Commercially available compounds were used as received
unless otherwise indicated. Saturated ammonium chloride (pH
∼8) was prepared by addition of 60 mL of aqueous ammonia
(25%) to 950 mL of saturated ammonium chloride. Phenylthio-
copper(I) was prepared according to Posner,18 copper(I) bro-
mide-dimethyl sulfide complex and copper(I) iodide were
prepared according to House,19 and commercial copper(I)
cyanide was oven-dried overnight at 150 °C and used without
any further purification. All reactions were carried out under
That the high Z-selectivity is peculiar to the stannyl-
cuprates is shown by the results gathered in Table 4. In
line with previous work4,14 a selection of Gilman (R2CuLi)
or Lipshutz (R2Cu(CN)Li2) reagents gave essentially 1:1
(14) For examples, see: (a) Marino, J . P.; Browne, L. J . Tetrahedron
Lett. 1976, 3245. (b) Yamamoto, Y.; Yatagai, H.; Maruyama, K. J . Org.
Chem. 1979, 44, 1744. (c) Fleming, I.; Perry, D. A. Tetrahedron 1981,
37, 4027 (stereoselective addition to a â-silyl alkynone). (d) Hashimoto,
S.; Sonegawa, M.; Sakata, S.; Ikegami, S. J . Chem. Soc., Chem.
Commun. 1987, 24. (e) Degl’Innocenti, A.; Stucchi, E.; Capperucci, A.;
Mordini, A.; Reginato, G.; Ricci, A. Synlett 1992, 332 (stereoselective
addition to a silyl alkynone with a terminal alkyne). (f) Houghton, T.
J .; Choi, S.; Rawal, V. H. Org. Lett. 2001, 3, 3615.
(15) Piers, E.; Tillyer, R. D. Can. J . Chem. 1996, 74, 2048.
(16) Takeda, T.; Kabasawa, Y.; Fujiwara, T. Tetrahedron 1995, 51,
2515.
(17) Nielsen, T. E.; Tanner, D. J . Org. Chem. 2002, 67, 6366.
(18) Posner, G. H.; Brunelle, D. J . Synthesis 1974, 662.
(19) House, H. O.; Chu, C.-Y.; Wilkins, J . M.; Umen, M. J . J . Org.
Chem. 1975, 40, 1460-1467.
1
mixtures of the E and Z products, as determined by H
NMR spectroscopy.
Ullenius4 and others14 have noted that it is in general
difficult to control the stereoselectivity of organocuprate
(12) Barbero, A.; Cuadrado, P.; Fleming, I.; Gonza´lez, A. M.; Pulido,
F. J . J . Chem. Soc., Chem. Commun. 1992, 351. Cuadrado, P.;
Gonza´lez-Nogal, A. M.; Sa´nchez, A. J . Org. Chem. 2001, 66, 1961.
(13) For preparation of such reagents, see: Piers, E.; Chong, J . M.;
Gustafson, K.; Andersen, R. J . Can. J . Chem. 1984, 62, 1.
7310 J . Org. Chem., Vol. 67, No. 21, 2002

Addition of Stannylcuprates to Alkynones
TABLE 2. Sta n n ylcu p r a tion of Alk yn on es II
entry
alkynone (R1, R2)
stannylcuprate
product (yield %)a,b
1
1e (Ph, (CH2)3OTBDMS)
1e
1f (Ph, (CH2)4OTBDMS)
1f
(Bu3Sn)(PhS)CuLi
(Bu3Sn)(PhS)CuLi
(Bu3Sn)(PhS)CuLi
(Bu3Sn)(Bu)Cu(CN)Li2
(Bu3Sn)(Bu)Cu(CN)Li2
(Bu3Sn)(PhS)CuLi
(Me3Sn)(PhS)CuLi
2e (92)
2e (11)
2f (>95)
2f (86)
2f (62)
2i (>95)
7 (79)
2c
3
4
5d
6
1f
1i (t-Bu, (CH2)2OTBDMS)
1i
7e
a
b
Isolated yield after flash column chromatography. None of the E isomers 3e,f,i and 8 could be detected. c The reaction was performed
in diethyl ether. Reaction performed with H2O (10 equiv) to quench the formed cuprate in situ. e Me3SnLi required for the cuprate
d
formation was generated by cleavage of hexamethylditin with MeLi (amine free reaction conditions).
TABLE 3. Sta n n ylcu p r a tion of Alk yn on es III
entry
alkynone (R1, R2)
1a (Ph, Bu)
1b (Ph, Ph)
1c (Ph, CH2OTBDMS)
1d (Ph, (CH2)2OTBDMS)
1e (Ph, (CH2)3OTBDMS)
1f (Ph, (CH2)4OTBDMS)
1g (Ph, CH(1-naphthyl)OTBDMS)
1h (cyclohexyl, (CH2)2OTBDMS)
1i (t-Bu, (CH2)2OTBDMS)
1j (i-Pr, (CH2)2OTBDMS)
1k (Et, (CH2)2OTBDMS)
product (yield %)a,b
F IGURE 1. Spectroscopic data for (Z)-â-tributylstannyl-R,â-
unsaturated ketones.
1
2
2a (95)
2b (92)
2c (78)
2d (>95)
2e (92)
2f (>95)
2g (41)
2h (>95)
2i (>95)
2j (>95)
2k (>95)
TABLE 4. Rea ction s of Com m on Cu p r a tes w ith
r,â-Acetylen ic Keton es
3
4c
5
6
7
8c
9c
10c
11c
a
b
None of the (E)-stereoisomers 3a -k could be detected. Iso-
lated yield after flash column chromatography. c Reactions were
also performed with methanol (1.7 equiv) to quench the formed
cuprate in situ, affording the Z-isomers 2d ,h -k exclusively,
although in lower yields.
an atmosphere of dry argon in carefully flame-dried glass-
ware. Argon gas was dried by passage through phosphorus
pentoxide and silica gel. Stannylcupration reactions were
routinely performed in Schlenk tubes, cautiously excluding
oxygen from the reaction mixture (important: the quality of
the tributyltin hydride batch was essential for the outcome of
these reactions).
Gen er a l P r oced u r e for Ad d ition of Lith iu m Acetylid es
to Wein r eb Am id es (A).20 The terminal alkyne (2.4 mmol)
was dissolved with stirring under nitrogen in THF (12 mL)
and cooled to -78 °C before addition of n-butyllithium (1.6 M
in hexanes, 1.6 mL, 2.6 mmol). The resultant solution was
stirred for 1 h at -78 °C, and a solution of the Weinreb amide
(1.2 mmol) in dry THF (2 mL) was added via a syringe. After
a
The products 9, 10, and 12 were obtained as E:Z ) ∼1:1
b
mixtures of isomers. Isolated yield after flash column chroma-
tography. c The products 9 and 10 could not be separated from
the substrate 1d , and the yields were therefore indicated by 1H
NMR.
1 h, the reaction was brought to room temperature and stirred
for an additional hour. Water was added and the phases were
separated. The aqueous phase was extracted with diethyl ether
(2 × 5 mL) and the combined organics were washed with water
(5 mL) and brine (2 × 5 mL), dried over magnesium sulfate,
and evaporated to dryness. The residue was purified by flash
(20) Nahm, S.; Weinreb, S. M. Tetrahedron Lett. 1981, 22, 3815.
J . Org. Chem, Vol. 67, No. 21, 2002 7311

Nielsen et al.
column chromatography on silica gel (hexane:ethyl acetate)
to give the alkynones 1a -k as colorless oils.
HRMS (FAB) calcd for C24H41O2SiSn [M - C4H9]+ 509.1902,
found 509.1891.
Gen er a l P r oced u r e for Son oga sh ir a Cou p lin g of Ter -
m in a l Alk yn es w ith Acid Ch lor id es (B).21 To a Schlenk
tube charged with freshly prepared copper(I) iodide (10 mg,
0.05 mmol), PdCl2(PPh3)2 (10 mg, 0.01 mmol), and the terminal
alkyne (2.5 mmol) was added triethylamine (5 mL), followed
by dropwise addition of the acid chloride (3.25 mmol) at room
temperature. The resulting dark solution turned yellow/orange
within a few hours of stirring with the formation of a large
precipitate. This was stirred overnight, whereafter water (5
mL) was added to the reaction mixture. The aqueous phase
was extracted with pentane (3 × 50 mL), and the combined
organics were washed with water (5 mL) and brine (5 mL),
dried over magnesium sulfate, filtered, and concentrated by
rotary evaporation. The residue was purified by flash column
chromatography on silica gel (hexane:ethyl acetate) to give the
alkynones 1a ,c-f,i as colorless oils.
Gen er al P r ocedu r e for Stan n ylcu pr ation of Alkyn on es.
A solution of diisopropylamine (142 mg, 1.4 mmol) in THF (7
mL) was cooled to 0 °C and n-butyllithium (1.6 M in hexanes,
0.9 mL, 1.4 mmol) was added dropwise via syringe. After 30
min of stirring, tributyltin hydride (349 mg, 1.2 mmol) was
added dropwise via syringe and stirring was continued at 0
°C for 30 min. The solution was cooled to -30 °C and solid
phenylthiocopper(I) (208 mg, 1.2 mmol) was added in one
portion. The mixture was stirred for 20 min at -30 °C to afford
a dark red solution of lithium (phenylthio)(tributylstannyl)-
cuprate. The reaction mixture was cooled to -78 °C before
dropwise addition of the alkynone (0.5 mmol) in THF (1.5 mL).
The reaction mixture was monitored by TLC, and when all
the starting material had reacted the reaction was quenched
by addition of saturated ammonium chloride (adjusted to pH
∼8 by addition of ammonium hydroxide) (10 mL) and diethyl
ether (50 mL). The mixture was washed several times with
saturated ammonium chloride (pH ∼8). The organic phase was
washed with brine, dried over magnesium sulfate, and filtered.
The solvent was evaporated and the residue purified by flash
chromatography on silica gel (hexane:ethyl acetate) to give the
(Z)-â-tributylstannyl-R,â-unsaturated ketones 2a -k as color-
less oils. Ad d ition of MeOH: Following the general procedure,
with the modification that MeOH (0.85 mmol) and the alkynone
(0.5 mmol) dissolved in the same THF solution (1.5 mL) were
added dropwise to the stannylcuprate reaction mixture.
Analytical data for compounds 2a -k and 7:
(Z)-5-(ter t-Bu tyl-dim eth yl-silan yloxy)-1-ph en yl-3-tr ibu -
tylsta n n a n yl-p en t-2-en -1-on e (2d ). Yield >95%; IR (CDCl3)
2955, 2928, 1652, 1234 cm-1 1H NMR (300 MHz, CDCl3) δ
;
7.94-7.90 (m, 2H), δ 7.76 (m, 1H), 7.58 (s, J (Sn-H) ) 110
Hz, 1H), 7.51-7.36 (m, 2H), 3.65 (t, J ) 7 Hz, 2H), 2.71 (t, J
) 7 Hz, J (Sn-H) ) 43 Hz, 2H), 1.46-1.36 (m, 6H), 1.29-1.16
(m, 6H), 0.96-0.90 (m, 6H), 0.93 (t, J ) 8 Hz, 3H), 0.82 (s,
9H), 0.80 (t, J ) 7 Hz, 3H), 0.00 (s, 6H); 13C NMR (75 MHz,
CDCl3) δ 189.4, 175.3, 138.3, 134.0, 132.5, 128.5, 128.4, 62.2,
43.8, 29.3, 27.5, 25.9, 18.3, 13.7, 11.2, -5.2; HRMS (FAB) calcd
for C25H43O2SiSn [M - C4H9]+ 523.2059, found 523.2075.
(Z)-6-(ter t-Bu tyl-dim eth yl-silan yloxy)-1-ph en yl-3-tr ibu -
tylsta n n a n yl-h ex-2-en -1-on e (2e). Yield 92%; IR (CDCl3)
2955, 2929, 1652, 1560, 1463, 1233 cm-1; 1H NMR (300 MHz,
CDCl3) δ 8.03 (m, 2H), 7.61 (s, J (Sn-H) ) 110 Hz, 1H), 7.59-
7.53 (m, 1H), 7.51-7.43 (m, 2H), 3.67 (t, J ) 7 Hz, 2H), 2.63
(t, J ) 8 Hz, 2H), 1.70 (m, J ) 7, 8 Hz, 2H), 1.57-1.42 (m,
6H), 1.35-1.25 (m, 6H), 1.10-0.80 (m, 15H), 0.93 (s, 9H), 0.08
(s, 6H); 13C NMR (75 MHz, CDCl3) δ 189.5, 179.6, 138.4, 132.4,
132.1, 128.4 (two peaks), 62.5, 37.3, 29.4, 27.5, 25.9, 18.4, 13.8,
11.2, -5.3; HRMS (FAB) calcd for C26H45O2SiSn [M - C4H9]+
537.2215, found 537.2224; Anal. Calcd for C30H54O2SiSn: C,
60.70; H, 9.19. Found: C, 60.99; H, 9.19.
(Z)-6-(ter t-Bu tyl-dim eth yl-silan yloxy)-1-ph en yl-3-tr ibu -
tylsta n n a n yl-h ep t-2-en -1-on e (2f). Yield >95%; IR (CDCl3)
2955, 2958, 1652, 1463, 1255 cm-1; 1H NMR (300 MHz, CDCl3)
δ 8.02-7.97 (m, 2H), 7.58 (s, J (Sn-H) ) 111 Hz, 1H), 7.61-
7.38 (m, 3H), 3.66 (t, J ) 6 Hz, 2H), 2.58 (t, J ) 6 Hz, J (Sn-
H) ) 43 Hz, 2H), 1.75-1.23 (m, 24H), 1.13-0.82 (m, 15H),
0.91 (s, 9H), 0.07 (s, 6H); 13C NMR (75 MHz, CDCl3) δ 189.6,
179.9, 138.5, 132.4, 132.1, 128.5, 128.4, 63.0, 40.9, 32.7, 29.4,
27.5, 26.0, 18.4, 13.7, 11.2, -5.2; HRMS (FAB) calcd for
C
27H47O2SiSn [M - C4H9]+ 551.2372, found 551.2377.
(Z)-4-(ter t-Bu tyl-d im eth yl-sila n yloxy)-4-n a p h th a len -1-
yl-1-p h en yl-3-tr ibu tylsta n n a n yl-bu t-2-en -1-on e (2g). Yield
41%; IR (CDCl3) 2954, 2927, 1653, 1464, 1229 cm-1; 1H NMR
(500 MHz, CDCl3) δ 8.39 (s, J (Sn-H) ) 103 Hz, 1H), 8.32-
8.24 (m, 1H), 8.14-8.05 (m, 2H), 7.92-7.72 (m, 2H), 7.64-
7.20 (m, 7H), 6.32 (s, J (Sn-H) ) 19 Hz, 1H), 1.24-0.96 (m,
12H), 0.91 (s, 9H), 0.80-0.60 (m, 15H), 0.12 (s, 3H), -0.09 (s,
3H); 13C NMR (125 MHz, CDCl3) δ 190.3, 177.8, 136.7, 134.3,
132.7, 131.3, 130.8, 129.1, 128.8, 128.7, 128.6, 127.6, 127.1,
125.6, 125.4, 125.0, 124.5, 78.4, 29.0, 27.3, 26.0, 18.4, 13.6, 11.0,
-4.1, -4.5; HRMS (FAB) calcd for C34H47O2SiSn [M - C4H9]+
635.2374, found 635.2385.
(Z)-7-(ter t-Bu tyl-d im eth yl-sila n yloxy)-1-cycloh exyl-3-
tr ibu tylsta n n a n yl-p en t-2-en -1-on e (2h ). Yield >95%; IR
(CDCl3) 2928, 1675, 1569, 1464, 1256 cm-1; 1H NMR (300 MHz,
CDCl3) δ 6.92 (s, J (Sn-H) ) 114 Hz, 1H), 3.64 (t, J ) 7 Hz,
2H), 2.65 (t, J (Sn-H) ) 43 Hz, 2H), 2.40 (m, J ) 11, 4 Hz,
1H), 1.87-1.76 (m, 2H), 1.74-1.57 (m, 2H), 1.50-1.19 (m,
18H), 1.05-0.80 (m, 15H), 0.91 (s, 9H), 0.06 (s, 6H); 13C NMR
(125 MHz, CDCl3) δ 202.7, 171.5, 136.4, 62.2, 50.6, 43.2, 29.3,
28.5, 27.5, 26.0, 25.9, 25.7, 18.3,13.7, 11.1, -5.3; HRMS (FAB)
calcd for C25H49O2SiSn [M - C4H9]+ 529.2528, found 529.2548.
Anal. Calcd for C29H58O2SiSn: C, 59.47; H, 10.00. Found: C,
59.54; H, 9.87.
(Z)-7-(ter t-Bu tyl-d im eth yl-sila n yloxy)-2,2-d im eth yl-5-
tr ibu tylsta n n a n yl-h ep t-4-en -3-on e (2i). Yield >95%; IR
(CDCl3) 2955, 2928, 1672, 1566, 1464, 1256 cm-1; 1H NMR (300
MHz, CDCl3) δ 7.13 (s, J (Sn-H) ) 114 Hz), 1H), 3.67 (t, J )
7 Hz, 2H), 2.67 (t, J ) 7 Hz, J (Sn-H) ) 44 Hz, 2H), 1.54-
1.23 (m, 12H), 1.17 (s, 9H), 1.03-0.82 (m, 15H), 0.90 (s, 9H),
0.06 (s, 6H); 13C NMR (75 MHz, CDCl3) δ 204.5, 171.3, 133.5,
67.4, 48.7, 47.7, 29.3, 27.5, 26.4, 25.9, 18.3, 13.7, 11.1, -5.2;
HRMS (FAB) calcd for C23H47O2SiSn [M - C4H9]+ 503.2371,
found 503.2373. Anal. Calcd for C27H56O2SiSn: C, 57.95; H,
10.11. Found: C, 58.07; H, 9.84.
(Z)-1-P h en yl-3-tr ibu tylsta n n a n yl-h ep t-2-en -1-on e (2a ).
Yield 95%; IR (CDCl3) 2956, 2872, 1651, 1560, 1464, 1234 cm-1
;
1H NMR (300 MHz, CDCl3) δ 8.03-7.97 (m, 2H), 7.59-7.43
(m, 3H), 7.56 (m, J (Sn-H) ) 110 Hz, 1H), 2.56 (t, J ) 7 Hz,
J (Sn-H) ) 44 Hz, 2H), 1.71-1.19 (m, 16H), 1.12-0.82 (m,
18H); 13C NMR (75 MHz, CDCl3) δ 189.5, 180.1, 138.4, 132.4,
132.1, 128.4, 128.3, 40.8, 31.6, 29.4, 27.5, 22.5, 14.0, 13.7, 11.2;
HRMS (FAB) calcd for C21H33OSn [M - C4H9]+ 421.1557, found
421.1548.
(Z)-1,3-Dip h en yl-3-tr ibu tylsta n n a n yl-p r op en on e (2b).
1
Yield 92%; IR (CDCl3) 2956, 1647, 1597, 1402, 1341 cm-1; H
NMR (300 MHz, CDCl3) δ 8.07-8.02 (m, 2H), 7.66 (s, J (Sn-
H) ) 101 Hz, 1H), 7.61-7.10 (m, 8H), 1.54-1.16 (m, 12H),
1.08-0.75 (m, 15H); 13C NMR (75 MHz, CDCl3) δ 190.0, 176.6,
146.6, 138.2, 134.0, 132.7, 128.6, 128.5, 128.1, 126.9, 126.2,
29.2, 27.4, 13.7, 12.1; HRMS (FAB) calcd for C23H29OSn [M -
C4H9]+ 441.1245, found 441.1269.
(Z)-4-(ter t-Bu tyl-dim eth yl-silan yloxy)-1-ph en yl-3-tr ibu -
tylsta n n a n yl-bu t-2-en -1-on e (2c). Yield 78%; IR (CDCl3)
2955, 2927, 1652, 1464, 1254 cm-1; 1H NMR (500 MHz, CDCl3)
δ 8.07-7.93 (m, 2H), 7.99 (s, J (Sn-H) ) 104 Hz, 1H), 7.63-
7.40 (m, 3H), 4.63 (br s, 2H), 1.57-1.38 (m, 6H), 1.35-1.20
(m, 6H), 1.08-0.78 (m, 15H), 0.95 (s, 9H), 0.13 (s, 6H); 13C
NMR (125 MHz, CDCl3) δ 193.9, 175.6, 138.5, 132.6, 128.5 (two
peaks), 127.7, 69.3, 29.3, 27.2, 26.0, 18.5, 13.7, 11.0, -5.2;
(Z)-7-(ter t-Bu tyl-dim eth yl-silan yloxy)-2-m eth yl-5-tr ibu -
tylsta n n a n yl-h ep t-4-en -3-on e (2j). Yield >95%; IR (CDCl3)
(21) Tohda, Y.; Sonogashira, K.; Hagihara, N. Synthesis 1977, 777.
7312 J . Org. Chem., Vol. 67, No. 21, 2002

Addition of Stannylcuprates to Alkynones
2956, 1680, 1457, 1256 cm-1 1H NMR (300 MHz, CDCl3) δ
6.92 (s, J (Sn-H))114 Hz, 1H), 3.65 (t, J ) 7 Hz, 2H), 2.66
(m, J ) 7, 7 Hz, J (Sn-H) ) 43 Hz, 3H), 1.53-1.20 (m, 12H),
1.12 (d, J ) 7 Hz, 6H), 1.01-0.81 (m, 15H), 0.90 (s, 9H), 0.06
(s, 6H); 13C NMR (75 MHz, CDCl3) δ 203.4, 171.7, 136.1, 62.1,
43.2, 40.5, 29.3, 27.4, 25.9, 18.2 (two peaks), 13.7, 11.0, -5.3;
HRMS (FAB) calcd for C22H45O2SiSn [M - C4H9]+ 489.2214,
found 489.2242.
(Z)-7-(ter t-Bu t yl-d im et h yl-sila n yloxy)-5-t r ib u t ylst a n -
n a n yl-h ep t-4-en -3-on e (2k ). Yield >95%; IR (CDCl3) 2956,
2927, 1684, 1570, 1464, 1256 cm-1; 1H NMR (500 MHz, CDCl3)
δ 6.87 (s, J (Sn-H) ) 111 Hz, 1H), 3.64 (t, J ) 7 Hz, 2H), 2.65
(t, J ) 7 Hz, J (Sn-H) ) 43 Hz, 2H), 2.49 (q, J ) 7 Hz, 2H),
1.56-1.20 (m, 12H), 1.11 (t, J ) 7 Hz, 3H), 1.01-0.80 (m, 15H),
0.90 (s, 9H), 0.06 (s, 6H); 13C NMR (75 MHz, CDCl3) δ 193.9,
171.1, 136.9, 62.1, 43.1, 36.2, 29.3, 27.5, 26.0, 18.3, 13.7, 11.0,
8.3, -5.3; HRMS (FAB) calcd for C21H43O2SiSn [M - C4H9]+
475.2058, found 475.2075.
;
CDCl3) δ 7.12 (s, J (Sn-H) ) 123 Hz, 1H), 3.67 (t, J ) 7 Hz,
3H), 2.69 (t, J ) 7 Hz, 2H), 1.17 (s, 9H), 0.89 (s, 9H), 0.13 (s,
J (Sn-H) ) 54 Hz, 9H), 0.05 (s, 6H); 13C NMR (75 MHz, CDCl3)
δ 204.7, 171.6, 133.2, 62.2, 43.1, 42.5, 26.4, 26.0, 18.3, -5.2,
-7.4; HRMS (FAB) calcd for
C
14H29O2SiSn [M - CH3]+
419.1431, found 419.1424.
Ack n ow led gm en t. We thank the Technical Uni-
versity of Denmark, The Danish Technical Research
Council, and the University of Salamanca (MACdD) for
financial support, Thomas Rossmeier and Peter Chris-
tensen for experimental assistance, and Prof. B. H.
Lipshutz for exchange of information.
Su p p or tin g In for m a tion Ava ila ble: Analytical data for
1
compounds 1c-k and H and 13C NMR spectra for compounds
2a -k and 7. This material is available free of charge via the
(Z)-7-(ter t-Bu tyl-d im eth yl-sila n yloxy)-2,2-d im eth yl-5-
tr im eth ylsta n n a n yl-h ep t-4-en -3-on e (7). Yield 79%; IR
(CDCl3) 2958, 1667, 1568, 1472, 1256 cm-1; 1H NMR (300 MHz,
Internet at http://pubs.acs.org.
J O0259008
J . Org. Chem, Vol. 67, No. 21, 2002 7313