Reactions of esters of (α-bromoacyl)acetic acids with sodium thioacetate

REACTIONS OF ESTERS OF (a-BROMOACYL)ACETIC ACIDS WITH SODIUM THIOACETATE S. I'. Zav'yalov, O. V. Dorofeeva, and O. K. Taganova UDC 542.91:547.733 We have found that the ethyl esters of (a-bromoacyl)acetic acids la-lc react with AcSNa in aqueous acetone at ~20"C to form 2-alkyl-3-hydroxy-$-carbethoxy-5-methylthiophenes IIIa- IIIc. This unusual conversion may be viewed as a two-step process involving the nucleo- philic substitution of a thioacetate group for the bromine atom followed by cyclization of the intermediate thioacetates (If): AcSNa C2H~OOCCH2COCHBrR - - ~ (Ia-c) R = Me (b), Et (b), Am-n (c) [C~HsOOCCH2COCH(SAc)R] C2H50OC ~ (II)oH \ / ;.A H3C S 1~ (Ilia-c) A solution of 16 g of ethyl (a-bromopropionyl)acetate (la) in I00 ml of acetone was given successive additions of 20 ml of water, i0 ml of AcSH, and NaaCOa to pH ~8.5 with stirring. The mixture was stirred for another 48 h at ~20~ diluted with water, stirred for i h, and extracted with ethyl acetate. The extract was dried by NaaSO~, and after the removal of the solvent, the residue was vacuum-distilled. This yielded 6.6 g (46%) of Ilia, bp 125-128~ (3 mm), mp 440C (from ether at --40~ UV spectrum (ethanol): ~max 214 and 256 nm. IR spectrum (KBr, ~, cm-~): 789 (thlophene ring, 1670 (C=O), 3240 (OH). PMR spectrum (CDaOD, 6, ppm): 0.90 (t, CHa), 1.80 and 2.30 (s, 2CH~), 4.20 (q, CHaO). Mass spec- + trum: :m/z 200 (M+), 154 (M+- CaHsOH), 127 (M+- COOC2H,), 45 (HC~S). Compounds lllb and lllc were obtained in a similar manner from ethyl (~-bromobutvryl)acetate and ethyl (a-bromoenanthoyl)acetate (Ib and Ic) with ~40% yields. Compound lllb, bp 140- 143~ (3 mm). UV spectrum (ethanol): %max 216 and 254 nm. IR spectrum (in a thin layer, ~, cm-1): 791, 1680, 3275. PMR spectrum (CCI~, 6, ppm): 1.30 (m, 2CH~), 2.55 (s, CHa), 2.71 (m, CHa), 4.28 (q, CH20). Compound lllc, bp 166-169~ (4 mm). UV spectrum (ethanol): ~nmx 217 and 250 nm. IR spectrum (in a thin layer, ~, cm-1): 792, 1680, 3293. PMR spectrum (CCI~, 6, ppm): 0.90 (m, 2CHa), 1.30 (m, CH2CHaCH2), 2.48 (br. s, CHa, CH2), 4.19 (q, CH20). The elemental analyses correspond to the empirical formulas of llla-lllc. N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, p. 1920, August, 1982. Original article submitted April 21, 1982. 1712 0568-5230/82/3108-1712507.50 1983 Plenum Publishing Corporation

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Transcript of Reactions of esters of (α-bromoacyl)acetic acids with sodium thioacetate

REACTIONS OF ESTERS OF (a-BROMOACYL)ACETIC ACIDS WITH SODIUM

THIOACETATE

S. I'. Zav'yalov, O. V. Dorofeeva, and O. K. Taganova

UDC 542.91:547.733

We have found that the ethyl esters of (a-bromoacyl)acetic acids la-lc react with AcSNa in aqueous acetone at ~20"C to form 2-alkyl-3-hydroxy-$-carbethoxy-5-methylthiophenes IIIa- IIIc. This unusual conversion may be viewed as a two-step process involving the nucleo- philic substitution of a thioacetate group for the bromine atom followed by cyclization of the intermediate thioacetates (If):

AcSNa C2H~OOCCH2COCHBrR - - ~

(Ia-c)

R = Me (b), Et (b), Am-n (c)

[C~HsOOCCH2COCH(SAc)R]

C2H50OC ~ (II)oH \ /

; .A H3C S 1~

(Ilia-c)

A solution of 16 g of ethyl (a-bromopropionyl)acetate (la) in I00 ml of acetone was given successive additions of 20 ml of water, i0 ml of AcSH, and NaaCOa to pH ~8.5 with stirring. The mixture was stirred for another 48 h at ~20~ diluted with water, stirred for i h, and extracted with ethyl acetate. The extract was dried by NaaSO~, and after the removal of the solvent, the residue was vacuum-distilled. This yielded 6.6 g (46%) of Ilia, bp 125-128~ (3 mm), mp 440C (from ether at --40~ UV spectrum (ethanol): ~max 214 and 256 nm. IR spectrum (KBr, ~, cm-~): 789 (thlophene ring, 1670 (C=O), 3240 (OH). PMR spectrum (CDaOD, 6, ppm): 0.90 (t, CHa), 1.80 and 2.30 (s, 2CH~), 4.20 (q, CHaO). Mass spec-

+ trum: :m/z 200 (M+), 154 (M +- CaHsOH), 127 (M +- COOC2H,), 45 (HC~S).

Compounds lllb and lllc were obtained in a similar manner from ethyl (~-bromobutvryl)acetate and ethyl (a-bromoenanthoyl)acetate (Ib and Ic) with ~40% yields. Compound lllb, bp 140- 143~ (3 mm). UV spectrum (ethanol): %max 216 and 254 nm. IR spectrum (in a thin layer, ~, cm-1): 791, 1680, 3275. PMR spectrum (CCI~, 6, ppm): 1.30 (m, 2CH~), 2.55 (s, CHa), 2.71 (m, CHa), 4.28 (q, CH20). Compound lllc, bp 166-169~ (4 mm). UV spectrum (ethanol): ~nmx 217 and 250 nm. IR spectrum (in a thin layer, ~, cm-1): 792, 1680, 3293. PMR spectrum (CCI~, 6, ppm): 0.90 (m, 2CHa), 1.30 (m, CH2CHaCH2), 2.48 (br. s, CHa, CH2), 4.19 (q, CH20). The elemental analyses correspond to the empirical formulas of llla-lllc.

N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, p. 1920, August, 1982. Original article submitted April 21, 1982.

1712 0568-5230/82/3108-1712507.50 �9 1983 Plenum Publishing Corporation