Carbonyl propargylation by 1-substituted prop-2-ynyl mesylates and carbonyl allenylation by 3-substituted prop-2-ynyl mesylates with tin(II) iodide and tetrabutylammonium iodide

Article abstract of DOI:10.1039/b006646j

1-Substituted prop-2-ynyl mesylates cause propargylation of aldehydes with tin(II) iodide, tetrabutylammonium iodide and sodium iodide in 1,3-dimethylimidazolidin-2-one to produce 2-substituted but-3-yn-1-ols, while 3-substituted prop-2-ynyl mesylates cau

Full text of DOI:10.1039/b006646j

Carbonyl propargylation by 1-substituted prop-2-ynyl mesylates and carbonyl
allenylation by 3-substituted prop-2-ynyl mesylates with tin(II) iodide and
tetrabutylammonium iodide
Yoshiro Masuyama,*† Akiko Watabe, Akihiro Ito and Yasuhiko Kurusu
Department of Chemistry, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
Received (in Cambridge, UK) 14th August 2000, Accepted 5th September 2000
First published as an Advance Article on the web 28th September 2000
1-Substituted prop-2-ynyl mesylates cause propargylation of
aldehydes with tin(II) iodide, tetrabutylammonium iodide
and sodium iodide in 1,3-dimethylimidazolidin-2-one to
produce 2-substituted but-3-yn-1-ols, while 3-substituted
prop-2-ynyl mesylates cause allenylation of aldehydes under
the same conditions as those of the propargylation by
1-substituted prop-2-ynyl mesylates to produce 2-substi-
tuted buta-2,3-dien-1-ols.
Alkynes and allenes have formed an attractive chemistry for
high reactivities with metal complexes or reagents.1 Thus, the
preparation of alkynes and allenes becomes an important theme.
Barbier-type carbonyl propargylation or allenylation with
propargylic halides is one of the most convenient methods for
the introduction of propargyl or allenyl functions.2–7 However,
it is not easy to control selectivity between Barbier-type
propargylation and allenylation with propargylic halides. We
have established both selective propargylation and allenylation
by 1-haloprop-2-yne with tin(II) halide and tetrabutylammon-
ium halide (TBAX) through choice of reaction conditions:
carbonyl propargylation occurs with 1-bromoprop-2-yne, SnCl2
and TBABr at 50 °C in water, while carbonyl allenylation
occurs with 1-chloroprop-2-yne, SnI2 and TBAI at 25 °C in
1,3-dimethylimidazolidin-2-one (DMI).8 1H NMR observations
(JEOL L-500) have confirmed that prop-2-ynyltriiodotin
(propargyltin), derived from 1-chloroprop-2-yne with SnI2 and
NaI at 25 °C in DMF-d7, does not isomerize to propa-
1,2-dienyltriiodotin (allenyltin) at 25 °C but does so at 50 °C.8,9
We thus hoped that this kind of isomerization of propargyltin to
allenyltin would be prohibited by the steric effect of a
3-substituent in 1-haloprop-2-ynes and be promoted by the
steric effect of a 1-substituent in 1-haloprop-2-ynes.10 We here
Table 1 Allenylation by prop-2-ynyl mesylate with SnI2 and TBAIa
Yield (%)b
2 + 3
R3
Time/h
2+3c
C6H5
ClC6H4
CH3OC6H4
CH3(CH2)5
c-C6H11
45
48
70
71
72
85
80
74
66
68
78+22
75+25
78+22
66+34
81+19
a The reaction of prop-2-ynyl mesylate (1.5 mmol) with aldehydes (1.0
mmol) was carried out using SnI2 (1.5 mmol), TBAI (0.10 mmol) and NaI
(1.5 mmol) in DMI (3 ml) at 10 °C. b Yields of a mixture of 2 and 3. c The
ratio was determined by 1H NMR analysis (JEOL L-500).
Table 2 Selective carbonyl propargylation or allenylation mediated by steric effectsa
Yield (%)b
2 + 3
R1
R2
R3
Time/h
2+3c
3 syn+antic
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
Pr
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
H
H
H
H
H
H
H
H
H
C6H5
ClC6H4
48
47
55
71
51
50
67
79
71
63
90
79
75
70
71
71
79
75
70
72
70
47
71
70
75
72
75
58
65
52
21d
62
57
65
41
81
84
76
56
32
35
48
71
83
65
41
75
66
55
48
44
66
85
41
~ 100+0
~ 100+0
~ 100+0
94+6
CH3C6H4
C6H5CHNCH
C6H5CH2CH2
CH2NCH(CH2)8
CH3(CH2)5
c-C6H11
90+10
89+11
90+10
84+16
~ 100+0
~ 100+0
~ 100+0
90+10
98+2
C6H5
ClC6H4
CH3C6H4
C6H5CH2CH2
CH2NCH(CH2)8
CH3(CH2)5
c-C6H11
C6H5
ClC6H4
CH3C6H4
2-Furyl
C6H5CHNCH
C6H5CH2CH2
CH2NCH(CH2)8
CH3(CH2)5
c-C6H11
C6H5
ClC6H4
CH3(CH2)5
98+2
93+7
12+88
6+94
49+51
48+52
47+53
50+50
47+53
19+81
26+74
35+65
6+94
0+ ~ 100
0+ ~ 100
1+99
1+99
10+90
14+86
2+98
e
—
H
H
H
48+52
50+50
22+78
Pr
Pr
1+99
8+92
a The reaction of 1- or 3-substituted prop-2-ynyl mesylates (1.5 mmol) with aldehydes (1.0 mmol) was carried out using SnI2 (2.0 mmol), TBAI (0.20 mmol)
and NaI (2.0 mmol) in DMI (3 ml) at rt. b Yields of a mixture of 2 and 3. c The ratios were determined by 1H NMR analysis (JEOL L-500). For the ratio
of syn to anti, see ref. 8. d The reaction was carried out in the presence of MS 4Å in THF. e The ratio was not confirmed.
DOI: 10.1039/b006646j
Chem. Commun., 2000, 2009–2010
This journal is © The Royal Society of Chemistry 2000
2009

carbonyl allenylation with SnI2 and TBAI. Thus, we invest-
igated whether the 1- or 3-substituents of prop-2-ynyl mesylates
affect the selectivity between propargylation and allenylation
under the same conditions as those of prop-2-ynyl mesylate (1;
R1, R2 = H) [eqn. (1)]. The results are summarized in Table 2.
3-Substituted prop-2-ynyl mesylates (1; R1 = H, R2 = CH3 and
R1 = H, R2 = C6H5) caused the same allenylation of various
aldehydes as that of 1 (R1, R2 = H). In particular, with aromatic
aldehydes, only allenyl carbinols 2 were obtained. The reaction
of cinnamaldehyde in DMI afforded 1-phenylhexa-1,3-dien-
5-one derivatives that were probably formed by the hydration of
the corresponding allenyl carbinols 2 (R2 = CH3, C6H5)
followed by dehydration.4,8 1-Substituted prop-2-ynyl mesylate
(1; R1 = CH3, R2 = H and R1 = Pr, R2 = H) caused the
preferential propargylation of various aldehydes. The selectiv-
ity for this propargylation was enhanced by the use of THF–
H2O (1+1) as a solvent instead of DMI: R1 = CH3, R2 = H, R3
= C6H5; rt, 72 h; 92%, 2 : 3 = 0 : ~ 100, syn+anti
46+54.
=
A plausible mechanism for the allenylation is illustrated in
Scheme 1. 3-Substituent R2 (CH3 or C6H5), being bulkier than
H, probably prohibits propargyltin intermediate A from iso-
merizing to allenyltin intermediate B. Thus allenyl carbinols 2
are produced more selectively than in the allenylation by prop-
2-ynyl mesylate (1; R1, R2 = H), via nucleophilic addition of
the propargyltin A at the g-position.8 A plausible mechanism for
the propargylation is illustrated in Scheme 2. 1-Substituent R1
(CH3 or Pr) probably promotes the isomerization of the initially
prepared propargyltin C to allenyltin D, even at room
temperature, or mediates a direct preparation of allenyltin D.§
The allenyltin D then undergoes nucleophilic addition to
aldehydes at the g-position to afford homopropargyl alcohols
3.
Scheme 1 Allenylation.
Notes and references
† E-mail: y-masuya@hoffman.cc.sophia.ac.jp
‡ The 1- or 3-substituted prop-2-ynyl mesylates were prepared from 1- or
3-substituted prop-2-yn-1-ols and methanesulfonyl chloride with triethyl-
amine in ether on an ice-bath. 1-Phenylprop-2-ynyl mesylate was not
prepared under the conditions described above: see I. S. Aidhen and R.
Braslau, Synth. Commun., 1994, 24, 789.
§ It was shown by 1H NMR analysis (JEOL L-500) that the reaction of
1-methylprop-2-ynyl mesylate with SnI2 and NaI in DMF-d7 produced
3-methylprop-1,2-dienyltriiodotin D (R1 = CH3) at 25 °C; d 1.73 (dd, J =
7.2, 2.6 Hz, 3H), 5.21 (quintet, J = 6.7 Hz, 1H), 6.09 (dq, J = 5.6, 2.6 Hz,
1H).
Scheme 2 Propargylation.
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report on selective Barbier-type carbonyl propargylation and
allenylation mediated by steric effects, using the 1- or
3-substituted prop-2-ynyl mesylates‡ as Barbier-type prop-
argylating or allenylating reagents, rather than the more usual
corresponding halides (1-haloprop-2-ynes), because the mesyl-
ates are superior to the halides for ease of preparation and the
stability of propargylic substrates.11
The reaction of prop-2-ynyl mesylate (1; R1, R2 = H) with
some aldehydes was carried out using SnI2, TBAI and NaI
under the same conditions as those reported for the carbonyl
allenylation by 1-chloroprop-2-yne [eqn. (1)].8 The results are
6 H. Tanaka, T. Hamatani, S. Yamashita and S. Torii, Chem. Lett., 1986,
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5550.
10 For selective formation of propargylmetals and allenylmetals utilizing
steric effects, see: J. Nokami, T. Tamaoka, T. Koguchi and R. Okawara,
Chem. Lett., 1984, 1939; L.-J. Zhang, Y.-Z. Huang and Z.-H. Huang,
Tetrahedron Lett., 1991, 32, 6579; S. Kobayashi and K. Nishio, J. Am.
Chem. Soc., 1995, 117, 6392.
(1)
11 For selective propargylation by propargylic mesylates with Et2Zn or InI
in the presence of PdII catalysts, see: J. A. Marshall and N. D. Adams,
J. Org. Chem., 1999, 64, 5201; J. A. Marshall and C. M. Grant, J. Org.
Chem., 1999, 64, 8214.
summarized in Table 1. Prop-2-ynyl mesylate (1; R1, R2 = H)
proved to be as available as 1-chloroprop-2-yne for the selective
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Chem. Commun., 2000, 2009–2010