- Email: [email protected]
Reaction of lithium 1-alkoxyeneselenolates with propargylic bromides: One-pot conversion to poly-substituted selenophenes
TetrahedronLetters,Vol. 36, No. 16, pp. 2807-2810, 1995 Pergamon
ElsevierScienceLtd Printed in Great Britain 0040-4039/95 $9.50+0.00 0040-4039(95)00402-5
Reaction of Lithium 1-Alkoxyeneselenolates with Propargylic Bromides: One-pot Conversion to Poly-substituted Selenophenes
Takahiro Kanda, Tatsuya Ezaka, Toshiaki Murai and Shinzi Kato*
Department of Chemistry, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-11, Japan
Abstract: Lithium 1-alkoxyeneselenolates 2 in tetrahydrofuran were characterized by 1H NMR for the first time. Their reaction with propargyl bromide was found to proceed through a propargylic rearrangement to generate allenic selenoic acid O-esters 3, which led to poly-substituted selenophenes in moderate yields under reflux.
Lithium enolates as a carbon nucleophile in their reaction with various carbon electrophiles to give asubstituted carbonyl compounds have widely been utilized for organic synthesis.l In contrast, the selenium counterparts of the nucleophiles have scarcely emerged in organic synthesis as well as in organoselenium chemistry 2-4 However, the selectivity of the reaction using lithium eneselenolates is of interest since they also belong to heteroatom-substituted ambident nucleophiles. Recently, we have described that in the reaction of lithium 1-alkylthioeneselenolates with allyl and propargyl bromides, the lithium eneselenolates act as a selenium nucleophile to give the corresponding Se-allyl and propargyl selenides, respectively. 5 Herein we report the first spectroscopic observation of tautomeric equilibrium of lithium 1-alkoxyeneselenolates, their reaction with propargylic bromides, and one-pot conversion to poly-substituted selenophenes.
Se a2-v,~oa
LDA 1 THF,-78 oC
-78 to temp °C ~
•
SeLi
OR 1 --.,/
1
R3C-CCH2 Br ~
2 Li
2'
2
/R 3 S.e ~'~'OR R2
R3
----
1+
3
~,
R2
Se R2~OR 4
(I) R3
+ 1
R10
OH 3 5
Lithium 1-alkoxyeneselenolates 2 as the starting material were readily prepared by the treatment of selenoesters 1 with lithium diisopropylamide (LDA). 6 Variable low temperature NMR spectra (d8-THF, from - 9 0 to 20 °C) of the eneselenolates 2 disclosed that an equilibrium between a selenoxo form (2') and a eneselenol one (2) lay so far to the latter species. 1H NMR spectra of 2 (RI= Me, R2= Ph, E/Z= 65/35) at -70 °C are shown in Fig. 1.7 This is the first spectroscopic characterization of eneselenol species 2. Next, treatment 2807
2808
of the nucleophiles 2 with propargyl bromide was found to form allenic selenoesters 3 as a major product. In these reactions, Se-propargylic selenides 4 were formed in only low yields (Table 1). For example (entry 1), to a THF solution of 2 (RI=Et, R2= Ph) at -78 °C, propargyl bromide was added. The mixture was warmed to 0 °C followed by stirring for 30 min. After washing with water and removal of the solvent at the same temperature, 1H NMR spectra of the residual substance revealed the formation of 3a (80 %) and 4a (10 %). Further purification by chromatography on silica gel at ca. 10 °C gave allenic selenoester 3a as a reddish yellow oil in 56 % isolated yield. Similarly, other allenic selenoesters 3 d - g were formed in 40-60 % (Table 1), whereas the isolation of the esters 3 d - g failed due to difficulty in chromatographic purification. 8,9 It is noted that this result is in large contrast with those of the reaction of the sulfur analogues such as R'CH=C(SR)SeLiI0 and R ' C H = C ( S R ) S K 1] with propargyl bromide giving Se- and S-propargylic products, respectively. When the reaction mixture was allowed to warm to 25 °C, selenophene 5a was produced in 4 1 % yield (entry 2). In
bH,
SeLi aE
\/
z
3
I
. . . .
bE
~
/
c E dE
cZ
dZ eZ/
i
9
J
. . . .
i
8
. . . .
i
7
.
.
.
.
8
I
. . . .
I
5
az
. . . .
a
Fig. 1 1H NMR Spectra of 2 (R~= Me, R2= Ph, E/Z= 65/35) Taken in ds-THF at -70 °C Table 1 Reactions of Lithium (E/Z)-l-Alkoxyeneselenolates with Propargylic Bromides b
entry
R1
R2
R3
temp, °C
1 2 3
Et
Ph
H H Me
0 25 0
4 5 6 7 8
Me Me /-Pr Bu Et
H H H H H
0 0 0 0 0
4-CLC6H 4 Ph Ph Ph Bu
3, %c
2a 4, %a,c
5, %c
3a,80 (56) d 4a,10 3a,38 4a,12 3b, 0 4b,-e(90)d
5a, 0 5a,41 5b, 0
3¢, 0 3d,51 3e, 63 3f, 62 3g, 62
5¢, 5d, 5e, 5f, 5g,
4c, 0 4d, 0 4e,28 4f, 21 4g,34
_e 9 0 0 0
a'rhe E/Z ratio of the compounds except 2 (R 1=Me, R2= Ph, 65/35) was not determined, bReaction conditions: R1CH2C(Se)OR 3 (1, 1 mmol), LDA (1 mmol), THF (10 mL) -78 o C, 20 min; R3 C~CCH2Br (1.0 mmol), 10 min; -78 o C to temp, 1 h; H20 (10 mL). c Based on 1 H NMR. d Isolated yield. e Not determined.
2809
the case of substituted propargylic bromide such as 1-bromobut-2-yne, only propargylic selenide 4b wasobtained (entry 3). The eneselenolate 2 (RI= Me, R2= 4-C1C6H4) gave a complex mixture containing 5c (entry 4). 12 1H NMR spectra of a crude mixture obtained from 2 and propargyl bromide (eq. 1) have indicated that no isomerization of 4 into selenoesters 3 takes place at the temperatures below 25 °C. This result suggests that the lithium eneselenolates 2 mainly act as a carbon nucleophile in the reaction under the described conditions. Presumably, the nucleophile 2 would attack the terminal acetylenic carbon of the propargylic bromides (propargylic rearrangement), leading directly to allenic selenoesters 3 not through the intermediate 4. In fact, the reaction with 1-bromobut-2-yne did not give allenic selenoesters 3, probably because the methyl group on the terminal acetylenic carbon of the bromide would hinder the attack of the eneselenolate 2.
1
LDA T H F , - 7 8 °C ~
R3C-=CCH 2Br - 7 8 to 67 °C 72 h
R2 ~ / R10
R3 CH 3
Isolated 5, % a: 62 ¢: 52 e: 54
b: 43* d: 60
(2)
*Based on 41a The isolated allenic selenoester 3a is labile toward oxygen and gradually decomposes at room temperature into an intractable oil, accompanying deposited elemental selenium. Under oxygen free and THF refluxing conditions, the ester 3a isomerizes to 5a. Thus, the reaction of 2 with propargylic bromides at higher temperature provides a facile and one-pot preparation of poly-substituted selenophenes 5 by the reaction of the nucleophiles 2 with propargylic bromides (eq. 2). 13 Isomerization of 4b to selenophene 5b also proceeded under similar refluxing conditions but required prolonged reaction time (12 days). In summary, the present findings have clarified a unique reactivity of selenium-substituted enolate nucleophiles. This would contribute to the development of the chemistry on heteroatom-substituted ambident anions. Acknowledgement, This work was supported by the Grant-in-Aid for Scientific Research on Priority Area of Reactive Organometallics and partially by the Grant-in-Aidfor Scientific Research provided by the Ministry of Education, Science and Culture, Japan. References
and Notes
(1) Trost, B. M.; Fleming, I. Comprehensive Organic Synthesis; Pergamon Press: Oxford, 1991, vol. 2, pp. 133-319; vol. 3, pp.l-63. (2) (a) Ogawa, A.; Sonoda, N. In Ref. 1, vol. 6, pp. 461-484; (b) Liotta, P. Ed. Organoselenium Chemistry; Wiley-Interscience: New York, 1987; (c) Kato, S.; Murai, T.; Ishida, M. Org. Prep. Proced. Int. 1986, 18, 369. (3) Organic synthesis using eneselenolates as nucleophiles: (a) Ref. 4c; (b) Vall6e Y.; Worrell, M. J. Chem. Soc., Chem. Commun. 1992, 1680; (c) Sukhai, R. S.; Brandsma, L. Synthesis 1979, 455. (4) Our recent researches on organoselenium chemistry: (a) Kageyama, H.; Kido, K.; Kato, S.; Murai, T. J. Chem. Soc., Perkin Trans. 1 1994, 1083; (b) Murai, T.; Mizutani, T.; Kanda, T.; Kato, S. J. Am. Chem. Soc. 1993, 115, 5823; (c) Kato, S.; Komuro, T.; Kanda, T.; Ishihara, H.; Murai, T. J. Am. Chem. Soc. 1993, 115, 3000; (d) Kanda, T.; Mizoguchi, K.; Koike, T.; Murai, T.; Kato, S. J. Chem. Soc., Chem. Commun. 1993, 1631; (e) Murai, T.; Hayashi, A.; Kanda, T.; Kato, S. Chem. Lett. 1993, 1469; (f) Ishihara, H.; Yoshimi, M.; Kato, S. Bull. Chem. Soc. Jpn. 1990, 61, 835. (5) The reaction of lithium 1-alkylthioeneselenolates with allyl bromide gave Se-allyl selenides, which quickly isomerized to y,6-unsaturated selenothioic acid S-alkyl esters by a seleno-Claisen rearrangement. 4c
2810
(6) Selenoesters 2 were synthesized by the procedure described in Ref. 4f. Other synthetic methods of 2: (a) Wright, S. W. Tetrahedron Lett. 1994, 35, 1331; (b) Segi, M.; Takahashi, T.; Ichinose, H.; Li, G. M.; Nakajima, T. Tetrahedron Lett. 1992, 33, 7865. See also Ref. 2a. (7) The stereochemistry of 2 (RI=Me, R2= Ph) was determined by comparison with that of the corresponding Se-methyl selenide prepared from methylation of 2. The ratio of E- and Z- isomers of 2 was unchanged during variable low temperature NMR studies. (8) Besides 3, 4 and 5, a small amount (0-10 %) of 2H-selenopyran derivatives were also obtained. (9) Selective spectral data for compounds: (2: RI=Me, R2= Ph): E-isomer: 1H NMR (ds-THF, 400 MHz): 6 3.83 (s, 3 H), 5.70 (s, 1 H), 6.71 (t, J = 7.3 Hz, 1 H) 6.99 (t, J = 7.3 Hz, 2 H), 7.32 (d, J = 7.3 Hz, 2 H); 13C NMR (d8-THF, 100 MHz): 6 57.8, 109.9, 121.4, 126.2, 128.1, 141.3, 166.1; 77Se NMR (d 8THF, 76 MHz): ~i 14.8; 7Li NMR (ds-THF, 155 MHz): 6 0.70; Z- isomer: 1H NMR: ~ 3.61 (s, 3 H), 5.94 (s, 1 H), 6.82 (t, J = 7.5 Hz, 1 H) 7.04 (t, J = 7.5 Hz, 2 H), 8.24 (d, J = 7.5 Hz, 2 H); 13C NMR: ~ 55.8, 104.4, 122.7, 127.2, 127.7, 141.7, 164.2; 77Se NMR: 8 61.7; 7Li NMR: 6 0.70; (3a): IR: (neat) 1956 (VC=C=C) cm-l; IH NMR (CDCI 3, 270 MHz): ~5 1.42 (t, J = 7.2 Hz, 3 H), 4.60 (q, J = 7.2 Hz, 2 H), 4.77 (dd, J = 6.6, 1.8 Hz, 2 H), 4.88 (dt, J = 8.5, 1.8 Hz, 1 H), 5.80 (dt, J = 8.5, 6.6 Hz, 1 H), 7.33-7.65 (m, 5 H); 13C NMR (CDC13, 68 MHz): 6 13.5, 73.2, 76.7, 91.0, 127.4, 127.9, 128.5, 138.6, 208.1,232.7. Anal. Calcd for CI3Hj3OSe: C, 58.87; H, 5.32. Found: C, 58.98; H, 5.35; (4a): Stereochemistry was not determined (Major/Minor= 75/25): Major: 1H NMR: 8 1.36 (t, J = 7.0 Hz, 3 H), 2.19 (t, J = 2.7 Hz, 1 H), 3.44 (d, J = 2.7 Hz, 2 H), 4.04 (q, J = 7.0 Hz, 2 H), 6.16 (s, 1 H), 7.15-7.82 (m, 5 H); Minor: 1H NMR: fi 1.35 (t, J = 7.0 Hz, 3 H), 2.28 (t, J = 2.7 Hz, 1 H), 3.39 (d, J = 2.7 Hz, 2 H), 4.10 (q, J = 7.0 Hz, 2 H), 6.38 (s, 1 H), 7.15-7.82 (m, 5 H); (Sa): IH NMR: 6 1.39 (t, J = 7.0 Hz, 3 H), 2.48 (d, J = 1.1 Hz, 3 H), 4.04 (q, J = 7.0 Hz, 2 H), 6.82 (d, J = 1.1 Hz, 1 H), 7.19 (t, J = 7.3 Hz, 1 H), 7.33 (t, J = 7.3 Hz, 2 H), 7.60 (d, J = 7.3 Hz, 2 H); 13C NMR: ~i 15.0, 18.3, 72.7, 122.9, 125.8, 126.6, 127.7, 128.2, 132.0, 135.6, 162.9. (10) In the reaction of R'CH=C(SR)SeLi with propargyl bromide, no allenic selenoester was detected. 4c ( l l ) T h e reaction of R'CH=C(SR)SK with propargyl bromide in liq. NH 3 gives S-propargyl sulfide, exclusively, although partial isomerization of the sulfide into allenic dithioester also occurs: (a) Schuijl, P. T. J.; Bos H. J. T.; Brandsma, L. Recl. Tray. Chim. Pays-Bas 1969, 88, 597; (b) Schuijl, R. T. W.; Brandsma, L. Recl. Trav. Chim. Pays-Bas 1968, 87, 929. (12) The reaction of more substituted propargylic halide such as 1-phenyl-3-chloropent-1-yne resulted in a complex mixture under the conditions. (13) Recently, synthesis of poly-substituted selenophenes has been reported by Nakayama: Nakayama, J.; Murai, F.; Hoshino, M.; Ishii, A. Tetrahedron Lett. 1988, 1399.
(Received in Japan 26 December 1994; revised 26 January 1995; accepted 22 February 1995)
ElsevierScienceLtd Printed in Great Britain 0040-4039/95 $9.50+0.00 0040-4039(95)00402-5
Reaction of Lithium 1-Alkoxyeneselenolates with Propargylic Bromides: One-pot Conversion to Poly-substituted Selenophenes
Takahiro Kanda, Tatsuya Ezaka, Toshiaki Murai and Shinzi Kato*
Department of Chemistry, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-11, Japan
Abstract: Lithium 1-alkoxyeneselenolates 2 in tetrahydrofuran were characterized by 1H NMR for the first time. Their reaction with propargyl bromide was found to proceed through a propargylic rearrangement to generate allenic selenoic acid O-esters 3, which led to poly-substituted selenophenes in moderate yields under reflux.
Lithium enolates as a carbon nucleophile in their reaction with various carbon electrophiles to give asubstituted carbonyl compounds have widely been utilized for organic synthesis.l In contrast, the selenium counterparts of the nucleophiles have scarcely emerged in organic synthesis as well as in organoselenium chemistry 2-4 However, the selectivity of the reaction using lithium eneselenolates is of interest since they also belong to heteroatom-substituted ambident nucleophiles. Recently, we have described that in the reaction of lithium 1-alkylthioeneselenolates with allyl and propargyl bromides, the lithium eneselenolates act as a selenium nucleophile to give the corresponding Se-allyl and propargyl selenides, respectively. 5 Herein we report the first spectroscopic observation of tautomeric equilibrium of lithium 1-alkoxyeneselenolates, their reaction with propargylic bromides, and one-pot conversion to poly-substituted selenophenes.
Se a2-v,~oa
LDA 1 THF,-78 oC
-78 to temp °C ~
•
SeLi
OR 1 --.,/
1
R3C-CCH2 Br ~
2 Li
2'
2
/R 3 S.e ~'~'OR R2
R3
----
1+
3
~,
R2
Se R2~OR 4
(I) R3
+ 1
R10
OH 3 5
Lithium 1-alkoxyeneselenolates 2 as the starting material were readily prepared by the treatment of selenoesters 1 with lithium diisopropylamide (LDA). 6 Variable low temperature NMR spectra (d8-THF, from - 9 0 to 20 °C) of the eneselenolates 2 disclosed that an equilibrium between a selenoxo form (2') and a eneselenol one (2) lay so far to the latter species. 1H NMR spectra of 2 (RI= Me, R2= Ph, E/Z= 65/35) at -70 °C are shown in Fig. 1.7 This is the first spectroscopic characterization of eneselenol species 2. Next, treatment 2807
2808
of the nucleophiles 2 with propargyl bromide was found to form allenic selenoesters 3 as a major product. In these reactions, Se-propargylic selenides 4 were formed in only low yields (Table 1). For example (entry 1), to a THF solution of 2 (RI=Et, R2= Ph) at -78 °C, propargyl bromide was added. The mixture was warmed to 0 °C followed by stirring for 30 min. After washing with water and removal of the solvent at the same temperature, 1H NMR spectra of the residual substance revealed the formation of 3a (80 %) and 4a (10 %). Further purification by chromatography on silica gel at ca. 10 °C gave allenic selenoester 3a as a reddish yellow oil in 56 % isolated yield. Similarly, other allenic selenoesters 3 d - g were formed in 40-60 % (Table 1), whereas the isolation of the esters 3 d - g failed due to difficulty in chromatographic purification. 8,9 It is noted that this result is in large contrast with those of the reaction of the sulfur analogues such as R'CH=C(SR)SeLiI0 and R ' C H = C ( S R ) S K 1] with propargyl bromide giving Se- and S-propargylic products, respectively. When the reaction mixture was allowed to warm to 25 °C, selenophene 5a was produced in 4 1 % yield (entry 2). In
bH,
SeLi aE
\/
z
3
I
. . . .
bE
~
/
c E dE
cZ
dZ eZ/
i
9
J
. . . .
i
8
. . . .
i
7
.
.
.
.
8
I
. . . .
I
5
az
. . . .
a
Fig. 1 1H NMR Spectra of 2 (R~= Me, R2= Ph, E/Z= 65/35) Taken in ds-THF at -70 °C Table 1 Reactions of Lithium (E/Z)-l-Alkoxyeneselenolates with Propargylic Bromides b
entry
R1
R2
R3
temp, °C
1 2 3
Et
Ph
H H Me
0 25 0
4 5 6 7 8
Me Me /-Pr Bu Et
H H H H H
0 0 0 0 0
4-CLC6H 4 Ph Ph Ph Bu
3, %c
2a 4, %a,c
5, %c
3a,80 (56) d 4a,10 3a,38 4a,12 3b, 0 4b,-e(90)d
5a, 0 5a,41 5b, 0
3¢, 0 3d,51 3e, 63 3f, 62 3g, 62
5¢, 5d, 5e, 5f, 5g,
4c, 0 4d, 0 4e,28 4f, 21 4g,34
_e 9 0 0 0
a'rhe E/Z ratio of the compounds except 2 (R 1=Me, R2= Ph, 65/35) was not determined, bReaction conditions: R1CH2C(Se)OR 3 (1, 1 mmol), LDA (1 mmol), THF (10 mL) -78 o C, 20 min; R3 C~CCH2Br (1.0 mmol), 10 min; -78 o C to temp, 1 h; H20 (10 mL). c Based on 1 H NMR. d Isolated yield. e Not determined.
2809
the case of substituted propargylic bromide such as 1-bromobut-2-yne, only propargylic selenide 4b wasobtained (entry 3). The eneselenolate 2 (RI= Me, R2= 4-C1C6H4) gave a complex mixture containing 5c (entry 4). 12 1H NMR spectra of a crude mixture obtained from 2 and propargyl bromide (eq. 1) have indicated that no isomerization of 4 into selenoesters 3 takes place at the temperatures below 25 °C. This result suggests that the lithium eneselenolates 2 mainly act as a carbon nucleophile in the reaction under the described conditions. Presumably, the nucleophile 2 would attack the terminal acetylenic carbon of the propargylic bromides (propargylic rearrangement), leading directly to allenic selenoesters 3 not through the intermediate 4. In fact, the reaction with 1-bromobut-2-yne did not give allenic selenoesters 3, probably because the methyl group on the terminal acetylenic carbon of the bromide would hinder the attack of the eneselenolate 2.
1
LDA T H F , - 7 8 °C ~
R3C-=CCH 2Br - 7 8 to 67 °C 72 h
R2 ~ / R10
R3 CH 3
Isolated 5, % a: 62 ¢: 52 e: 54
b: 43* d: 60
(2)
*Based on 41a The isolated allenic selenoester 3a is labile toward oxygen and gradually decomposes at room temperature into an intractable oil, accompanying deposited elemental selenium. Under oxygen free and THF refluxing conditions, the ester 3a isomerizes to 5a. Thus, the reaction of 2 with propargylic bromides at higher temperature provides a facile and one-pot preparation of poly-substituted selenophenes 5 by the reaction of the nucleophiles 2 with propargylic bromides (eq. 2). 13 Isomerization of 4b to selenophene 5b also proceeded under similar refluxing conditions but required prolonged reaction time (12 days). In summary, the present findings have clarified a unique reactivity of selenium-substituted enolate nucleophiles. This would contribute to the development of the chemistry on heteroatom-substituted ambident anions. Acknowledgement, This work was supported by the Grant-in-Aid for Scientific Research on Priority Area of Reactive Organometallics and partially by the Grant-in-Aidfor Scientific Research provided by the Ministry of Education, Science and Culture, Japan. References
and Notes
(1) Trost, B. M.; Fleming, I. Comprehensive Organic Synthesis; Pergamon Press: Oxford, 1991, vol. 2, pp. 133-319; vol. 3, pp.l-63. (2) (a) Ogawa, A.; Sonoda, N. In Ref. 1, vol. 6, pp. 461-484; (b) Liotta, P. Ed. Organoselenium Chemistry; Wiley-Interscience: New York, 1987; (c) Kato, S.; Murai, T.; Ishida, M. Org. Prep. Proced. Int. 1986, 18, 369. (3) Organic synthesis using eneselenolates as nucleophiles: (a) Ref. 4c; (b) Vall6e Y.; Worrell, M. J. Chem. Soc., Chem. Commun. 1992, 1680; (c) Sukhai, R. S.; Brandsma, L. Synthesis 1979, 455. (4) Our recent researches on organoselenium chemistry: (a) Kageyama, H.; Kido, K.; Kato, S.; Murai, T. J. Chem. Soc., Perkin Trans. 1 1994, 1083; (b) Murai, T.; Mizutani, T.; Kanda, T.; Kato, S. J. Am. Chem. Soc. 1993, 115, 5823; (c) Kato, S.; Komuro, T.; Kanda, T.; Ishihara, H.; Murai, T. J. Am. Chem. Soc. 1993, 115, 3000; (d) Kanda, T.; Mizoguchi, K.; Koike, T.; Murai, T.; Kato, S. J. Chem. Soc., Chem. Commun. 1993, 1631; (e) Murai, T.; Hayashi, A.; Kanda, T.; Kato, S. Chem. Lett. 1993, 1469; (f) Ishihara, H.; Yoshimi, M.; Kato, S. Bull. Chem. Soc. Jpn. 1990, 61, 835. (5) The reaction of lithium 1-alkylthioeneselenolates with allyl bromide gave Se-allyl selenides, which quickly isomerized to y,6-unsaturated selenothioic acid S-alkyl esters by a seleno-Claisen rearrangement. 4c
2810
(6) Selenoesters 2 were synthesized by the procedure described in Ref. 4f. Other synthetic methods of 2: (a) Wright, S. W. Tetrahedron Lett. 1994, 35, 1331; (b) Segi, M.; Takahashi, T.; Ichinose, H.; Li, G. M.; Nakajima, T. Tetrahedron Lett. 1992, 33, 7865. See also Ref. 2a. (7) The stereochemistry of 2 (RI=Me, R2= Ph) was determined by comparison with that of the corresponding Se-methyl selenide prepared from methylation of 2. The ratio of E- and Z- isomers of 2 was unchanged during variable low temperature NMR studies. (8) Besides 3, 4 and 5, a small amount (0-10 %) of 2H-selenopyran derivatives were also obtained. (9) Selective spectral data for compounds: (2: RI=Me, R2= Ph): E-isomer: 1H NMR (ds-THF, 400 MHz): 6 3.83 (s, 3 H), 5.70 (s, 1 H), 6.71 (t, J = 7.3 Hz, 1 H) 6.99 (t, J = 7.3 Hz, 2 H), 7.32 (d, J = 7.3 Hz, 2 H); 13C NMR (d8-THF, 100 MHz): 6 57.8, 109.9, 121.4, 126.2, 128.1, 141.3, 166.1; 77Se NMR (d 8THF, 76 MHz): ~i 14.8; 7Li NMR (ds-THF, 155 MHz): 6 0.70; Z- isomer: 1H NMR: ~ 3.61 (s, 3 H), 5.94 (s, 1 H), 6.82 (t, J = 7.5 Hz, 1 H) 7.04 (t, J = 7.5 Hz, 2 H), 8.24 (d, J = 7.5 Hz, 2 H); 13C NMR: ~ 55.8, 104.4, 122.7, 127.2, 127.7, 141.7, 164.2; 77Se NMR: 8 61.7; 7Li NMR: 6 0.70; (3a): IR: (neat) 1956 (VC=C=C) cm-l; IH NMR (CDCI 3, 270 MHz): ~5 1.42 (t, J = 7.2 Hz, 3 H), 4.60 (q, J = 7.2 Hz, 2 H), 4.77 (dd, J = 6.6, 1.8 Hz, 2 H), 4.88 (dt, J = 8.5, 1.8 Hz, 1 H), 5.80 (dt, J = 8.5, 6.6 Hz, 1 H), 7.33-7.65 (m, 5 H); 13C NMR (CDC13, 68 MHz): 6 13.5, 73.2, 76.7, 91.0, 127.4, 127.9, 128.5, 138.6, 208.1,232.7. Anal. Calcd for CI3Hj3OSe: C, 58.87; H, 5.32. Found: C, 58.98; H, 5.35; (4a): Stereochemistry was not determined (Major/Minor= 75/25): Major: 1H NMR: 8 1.36 (t, J = 7.0 Hz, 3 H), 2.19 (t, J = 2.7 Hz, 1 H), 3.44 (d, J = 2.7 Hz, 2 H), 4.04 (q, J = 7.0 Hz, 2 H), 6.16 (s, 1 H), 7.15-7.82 (m, 5 H); Minor: 1H NMR: fi 1.35 (t, J = 7.0 Hz, 3 H), 2.28 (t, J = 2.7 Hz, 1 H), 3.39 (d, J = 2.7 Hz, 2 H), 4.10 (q, J = 7.0 Hz, 2 H), 6.38 (s, 1 H), 7.15-7.82 (m, 5 H); (Sa): IH NMR: 6 1.39 (t, J = 7.0 Hz, 3 H), 2.48 (d, J = 1.1 Hz, 3 H), 4.04 (q, J = 7.0 Hz, 2 H), 6.82 (d, J = 1.1 Hz, 1 H), 7.19 (t, J = 7.3 Hz, 1 H), 7.33 (t, J = 7.3 Hz, 2 H), 7.60 (d, J = 7.3 Hz, 2 H); 13C NMR: ~i 15.0, 18.3, 72.7, 122.9, 125.8, 126.6, 127.7, 128.2, 132.0, 135.6, 162.9. (10) In the reaction of R'CH=C(SR)SeLi with propargyl bromide, no allenic selenoester was detected. 4c ( l l ) T h e reaction of R'CH=C(SR)SK with propargyl bromide in liq. NH 3 gives S-propargyl sulfide, exclusively, although partial isomerization of the sulfide into allenic dithioester also occurs: (a) Schuijl, P. T. J.; Bos H. J. T.; Brandsma, L. Recl. Tray. Chim. Pays-Bas 1969, 88, 597; (b) Schuijl, R. T. W.; Brandsma, L. Recl. Trav. Chim. Pays-Bas 1968, 87, 929. (12) The reaction of more substituted propargylic halide such as 1-phenyl-3-chloropent-1-yne resulted in a complex mixture under the conditions. (13) Recently, synthesis of poly-substituted selenophenes has been reported by Nakayama: Nakayama, J.; Murai, F.; Hoshino, M.; Ishii, A. Tetrahedron Lett. 1988, 1399.
(Received in Japan 26 December 1994; revised 26 January 1995; accepted 22 February 1995)