Aliphatic Chemistry of Fluorene: Part Ix. Some Bifunctional Derivatives

Abstract

AIethyl phenanthrene-9-carboxylate, dimcthyl phennnthrene-9,10-clica~rbo~yII~te, and N,Ndimethyl phenanthrene-9-cc~rboxX~~~~ic1e ha\e been prepared directly from fluorene bl a noxel route. Neighboring group participation b) carbomethosy has been clearly demonstrated in the reactions of some 9,9-disubstituted fluorencs.This paper describes the preparation and reactions of a number of fluorene derivatives having two functional groups in the 9-position. The ultimate objective has been to provide a synthesis of 4-nitrophenanthrene from 4-nitrofluorene. As a necessary preliminary to experiillents with nitrofluorenes, a route has been worlted out t o phenanthrei~e derivatives from fluorene ~vithout using reducing agents a t any stage.The forination of phenanthrene derivatives from substituted fluorenes is illustrated in Fig. 1. The group R may be hydrogen, alltyl, or arj.1 and S nlay be chlorine, bromine, hydrox) 1, p-tol~~enes~~lphonate, or similar leaving group. (For t~ pica1 references see 1 , 2 , 3.) Examples where R is a functional group have not been recorded and are rare in the broad field of \f7agner-1leer.ivein rearrangements. AIethyl fluorene-9-carbox!~late (Ia) was chosen as starting point for these experiments because it is highly reactive (4, 5) and carboxyl groups are readily eliminated from phenanthrene carboxylic acids (6, 7). Initially, experiments were made wit11 derivatives of the hydrosy-ester (Ib). These were not successful and are briefly summarized later in this paper. AIore subtle methods appeared neccssarland attention was turned to halo-esters. The bromo-and chloro-esters ((Ic) and (Id) respectively) were prepared in excellent yields froin the appropriate dil~alometl~,~i~es. As expected, bromo-ester (Ic) failed to react with a further molecule of fluorenc ester and was recovered ~lnchanged after it was heated with sodiuim iodide in illethyl ethyl ketone. I t Ivas also unchanged after it was heated in 98% formic acid or dimetl~ylformamlide or alone a t 220°. Like other neopentjll-type halides it reacted rapidly in the presence of silver ions,.' for example \vitl~ silver trifluoracetate in trifluoracetic acid to give diester (Ie). The diester (Ie) did not decompose a t 220° but solvolyzed smootl~ly in 987" formic acicl, giving methyl phenant11rene-9-carbou).late in 80% yield. Since Pschorr (6) saponified l31licl1 of tlre work znas carrted o l~t at The Unraers~ty, IItrll, during tlze tenure of a n I.C.I. F e l l o~~s k~p .