Succinic acids thiophenes

VOLHARDT ERDMANN Thiophene synthesis Thiophene synthesis from succinic acids... 

The pronounced influence of the phenyl group on optical activity led Fredga and Palm" to initiate an investigation on the optical activity of thiophene derivatives, in order to use this physical property for the elucidation of the aromatic character of thiophene. 2-(27) and 3-Thenylsuccinic acid (28), 2- (29) and 3-thienyl-succinic acid (30), 2- (31) and 3-thienylglycolic acid (32), 2-(33) and 3-a-methoxythienylacetie acid (34), -phenyl 2-thienyl-glycolic acid (35), -(2-thienyl)-y5-phenylpropionic acid (36), a-phenyl- -(2-thienyl) propionic acid (37), a,/ -di (2-thienyl)propionic acid (38) have been resolved into antipodes with the help of optically active bases. 

Cagniant and Cagniant have reported that succinoylation of benzo[6]thiophene under Friedel-Crafts conditions yields a separable mixture of the y-ketobutyric acids 42a and 43a in a ratio of 9 1 (combined yield 85%). Huang-Minlon reduction of 42a to the butyric acid (90%) followed by cyclization of the derived acid chloride (90%) was reported to yield 4-keto-l,2,3,4-tetrahydrodibenzothiophene (44a) (69% overall). Likewise, acylation of benzo[6]thiophene with the ester chloride of succinic acid in carbon disulfide-aluminum chloride gave a separable mixture (80%) of the 2- and 3-y-ketobutyric esters. Two alternative... 

Octahydrodibenzothiophene (73) has been prepared by the following sequence. Friedel-Crafts acylation of 4,5,6,7-tetra-hydrobenzo[6]thiophene with succinic anhydride (87%) or with the ester chloride of succinic acid followed by hydrolysis (80%), yields the keto acid (74). Huang-Minlon reduction of 74 followed by cyclization of the derived acid chloride with stannic chloride yields l-keto-1,2,3,4,6,7,-8,9-octahydrodibenzothiophene (53) (Section V,A). Reduction of 53 gives 73 as a solid (overall yield 32%). 

The original Paal reactions involved heating succinic acid or derivatives neat with P4S10 in a clay vessel, followed by crushing the vessel and extracting the tars to isolate the thiophene derivatives. Yields tended to be low. It was later shown that salts of the acids gave better yields, especially when lower sulfides of phosphorus were used, thus producing... 

Monoacetals of substituted succinaldehydes (162), readily prepared by hydroformylation of optically active a,(3-unsaturated aldehyde acetals, were used to synthesize 3-substituted thiophenes having an optically active substituent (163). In these cases, while the use of hydrogen sulfide and HC1 in methanol at room temperature was more convenient, comparison with formation of (163) by the Paal synthesis from an appropriately substituted succinic acid salt gave products having about the same amount of racemization (73JOC2361). 

Sodium amalgam serves to reduce selectively the double bond in an olefinic acid containing the thiophene or furan ring. " This reagent is also employed to prepare olefinic acids by partial reduction of certain polyenoic acids, e.g., 3-pentenoic acid (60%) from vinylacrylic acid. Among the dibasic acids prepared by this method are succinic acid from maleic acid (98%) by catalytic hydrogenation over Raney nickel catalyst and alkylsuccinic acids from alkenylsuccinic acids made by the Diels-Alder reaction of simple olefins and maleic anhydride. ... 

While caoutchouc was first obtained by polymerizing isoprene it has been found that other hydrocarbons containing the buta i-ydi-ene group will likewise yield caoutchouc. Such hydrocarbons have been obtained from several sources, e.g., turpentiney petroleuniy coaly acetylene. Also compounds related to succinic acid, e.g., pyrotartaric acid (methyl succinic acid) are possible of transformation into isoprene. Levulinic acid, which is aceto propionic acid, CHa—CO—CH2—CH2—COOH, yields a cyclic sulphur compound, methyl-thiophen (p. 853), which, like methyl pyrrolidine, yields isoprene. Ethyl alcohol by conversion into acetone and then by aldol condensation with ethane yields 2-methyl buta 2-ene, CHa—C = CH—CHa which may be transformed... 

The synthesis of thiophen which proves its constitution is from succinic acid by the action of phosphorus penta-sulphide. 

The homopolymer (PSATE) and copolymer P (SATE-co-Th) of succinic acid bis(2-thiophen-3-ylethyl) ester with thiophene obtained by Sacan et al. showed a contrast of 16 and 34 % and response times of 2.3 and 1.5 s, respectively, indicating that the copolymer had a shorter response time, higher contrast and higher stability. These polymers may serve as anodically coloring materials for use in ECD applications [62]. 

Friedel-Crafts acylation of benzo[6]thiophene and its derivatives with succinic anhydride132,439,662,663 or the ester chloride of succinic acid614, 618, 650,662 gives a y-keto acid (or ester), which is reduced to the corresponding y-(benzo[6]thienyl)butyric acid by the Huang Minion or Clemmensen method. y-(Benzo[6]thienyl)butyric acids may alternatively be prepared by the diethyl malonate synthesis on the appropriate halide,439,499 by the Arndt-Eistert reaction on the corresponding propionyl chloride,409,618 or by cyclization.347,618 The ketones (317 R = Hor OMe)347 have been prepared by cyclization... 

Dibenzothiophene derivatives are available from benzo[Z>]thiophenes by this procedure. In this case the major product of Friedel-Crafts acylation is the 3-substituted derivative (cf. Chapter 3.14) and reaction of sucdnic anhydride gives as the major product the keto acid (319), which is then reduced and cyclized via the acid chloride to 4-keto-l,2,3,4-tetrahydrodibenzothiophene (320). Better yields were obtained when 3-methoxycar-bonylpropionyl chloride was substituted for succinic anhydride in the first step (69JHC771). 

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