the Iieformatsky reaction' discouraged further exploration of this met,hod. Several other alternative routes were also considered but discarded, including the aluminum isopropoxide reduct'ioii of 1,l-dichloro-5oxo-3-phenyl-1,3-pentadiene to the 5-hydroxy compound followed by acid hydrolysis to the 5-phenyl-2,4pentadienoic acid,8 and the condensation of a cinnainaldehyde with ethyl acetate in the presence of 2 equiv of lit,hium amide in liquid ammoniag or sodium ethoxide. lo Bohlniann,7 in an extension of the reaction devised by Wittig arid Haag," successfully converted a series of aromatic aldehydes to the ;,-pheiiyl-2,3-pentadieii~)i(~ acid methyl esters by treatment with the tripheriyl phosphonium salt of methyl y-bromocrotorinte arid sodium niethoxide. ;\lodificaations of this tcchtiiquc \\ere cluicli to appear. Thus H o ~ ~ i eetr , shoncd that the cwndensatioii of benzaldehyde with dipheiiyl methyl phosphonocrot'onate in toluene a t 180" for 10 h r using potassium t-butoxide as the base afforded, after saponification, 52% of ;,-pheiiS'1-2,4-peiitadieii(Jic acid. Other worliers demonstrated that' either the triphenylphosphonium r e a g e r i t ~ lor~ ~the ~ ~alkyl phosphonates15j16could be used to convert cinnamaldehydes to the ;,-aryl-2,4-pentadienoic esters utilizing a variety o f bases :uid solvent systems. This lvorli \vas also exte1ided17 to the use of (trialliylanii1io)phosphotiiu~i re:geiits, but this approach seems to offer no particular advantage over the other available combinations:. Iteceiitly Wadsn orth arid Emmons'* demonstrated that phosphonate anions possessed significant advantages over the triaryl phosphoraries or "Wittig" reagents in that they were less expensive, reacted with a wider variety of ketones and aldehydes, and worked under milder conditions. Therefore, the experimental c*onditioiisemployed by these authors, L e . , the reacttion of triethyl phosphotioacetate iii 1,2-dimethoxyetha11c u4tig sodium hydride, nere extended to the prepiirat ioii i f the tlcsirctl 3-aiy1-2,3-peiitadiciioit, acids. The rc:tctioii of triethyl 4-phosphoriocrotoriate (III)Iy15 ith a series of s u b h t u t e d benzaldehydes under these (*onditions led smoothly to the desired ethyl esters (IV) (Table I), generally in yields of 50-80%. The method failed with p-nitrobenzaldehyde, but' in this case the desired product was obtained from triethyl phosphonoacetate and p-nitrocinnamaldehyde. The only att i ) I:. I%ulilitiarru, ('I,C,III, N c r . , 90, l 5 l U 11!).5i), ( 8 ) L. I . %akliar.kiii atid L. 1'. Sorokiiia. l m . .Ikcid. .\ciiik SSSW. Old. him. N , i i i k , !i:36 ( 1 9 5 9 ) : Clrem. Atslr., 64, 140P/ (l9tiO). (9) \\, K. Uunnavant a n d C . K . Hauser. J . O r y . Chrm., 25, 30:3 (l!ltiO), (10) V. N . I3elo\. and E. I. Shepelenkora, T r . Vses. I n s t . Sintetich. i Yaturul llushistykh I'ishchesto., 24 (1955); Chem. Abstr., 61, 17818c (1957). (11) G. \\itfig and T \ . Haag, Chem. Ber., 88, 1654 (1955). (12) L. Horner, H . Hoffmann, H . G. Wippel, and G. Iilahre, i h i d . , 92, 2499 (19.59). (1:3) I D
C
H
O f ( CLHSO)iPOCM?CH=CHCOLC?II ~
X
-
I11
-
CH=CHCH=CHCO-C-H,
KOH
X IV
1. soci.
CH=CHCH=CHCOIH
2, HK;R,R,*
X V
VI
tcllllJt t ( i al>k)ly t l l C IllCtllOCl t 0 Lll'OlllLtt~i(' kCt,l)llC'S \V;LS successful. Thus, p-c~hloroiiccto~,hc~io~ic \\:is cotrvcrtcd to ~-(p-clilorophciiyl)sorbic acid (VU) uiu the ethyl
ester. c~+ECHCH=cHco2H VI1
The iiiterniediatc esters IT' were readily hytlrolyxctl t o the acids T' (Table 11) with methanolic potassiuni hydroxide. I n those cases where the crude ester \\as obtained as an oil or a semisolid, it ~vitsconverted directly to the wid without, further purification. The early 1 i t e r a t ~ i - eindicated ~~ that 5-phenyl-2,4pentadienoic acid could not be converted to its acid chloride by the usual procedures, although later a ~ t h o r s ~reported ~ , ~ ~ the ~ ? successful ~ isolation of such materials. R e have also found that, in general, the acids can be converted satisfactorily to the acid (ahlorides by heating in excess thioriyl chloride for 2-5 hr. Since it \vas usually difirult to obtain the avid vhloritlcs in a state of aii:ilyticd purity, the isolatioii I)rocwlurc generally involved removal of excess thioiryl rliloritlc in L"XO followed by a single recrystallizat ioii from heptane to separate the product from unchnnged acid. If the acid chloride failed to crystallize, the heptane \vas removed arid the crude product TWS u s d as is. 5- [p-(Diniethylamino)pheriyl]-2,4-peiitadienoic~ :wid did not prove amenable to this technique hut w t s s i i ( ~ e s s fully converted to its acid chloride with oxalyl chloritic. The iwid chlorides were c*onvertetl readily to thc desired aiiiitles (Tahle 111) liy stirring with cs('css :mitic :it room teriil)cr;tt ~ r iisi c t ig \ ~ ( ~ i i x r ~[ri cr ~( ~ x r c w :iiiiiiic iis solvent. p - ~ ~ ~ i l o r o - ~ ~ - i s o ~ ~ r ~ ~ ~ ~ ~ l ~ ~ i ~ (1'111) was prepared in a similar maimer. hn nttenlpt CI-@CH=CHCO~HCH(CH~~~ VI11
to syiithwize S - i s o ~ ~ r o p y l - ~ - p l i c i i y l - ~ , ~ - ~ ~ e ~ i t : t t l i ~ ~ r : t ~ ~ i i (29) from ;,-pheiiyl-Z,~-peritadieiioi~ acid :itid isopi.ol)ylaiiiinc using S,i\"-dicyclohexylc.arbotliinlitle ~5 tlic? coridensirig agent, gave only 1,:~-dicycloliexyl-l-(T,phenyl-2,4-pent adienoy1)uren. Although several simple amides of S-phcnyl-2,4-per~tadieiioic acid have lxxn l)rtq):trc~li r t low yicltl hy hcxtiiig thc nitdhyl wtcr : i i i d (20) I\-.Tlgmek and IC. Stokloia, 1 ) i s s r r t i i t i o w s 1'h
