THE REACTIONS OF ORTHO ESTERS WITH CERTAIN ACID ANHYDRIDES^*

Abstract

Years ago Sawitsch reported that ethyl orthoformate had reacted with acetic anhydride1 to give, not methylidene acetate (CH(OOCCHs)j) as had been expected, but instead formic acid and ethyl acetate. Undoubtedly ethyl formate was formed at the same time.Later Claisen made use of acetic anhydride in the reaction between ethyl orthoformate and ethyl acetoacetate.2•3 In this reaction the product was ethyl -ethoxymethyleneacetoacetate and it has been tacitly assumed that the function of the acetic anhydride was to remove ethyl alcohol, thus permitting the reaction to proceed. This type of reaction works equally well with acetylacetone2 or with diethyl malonate,2 although in the latter case Claisen used zinc bromide as a catalyst.More recently Sah extended this type of condensation to prepare the corresponding products using, instead of the orthoformate the orthoacetate and the orthobenzoate.4 These reactions were also carried out in the presence of acetic anhydride.• Abstracted from the thesis presented by the second author to the faculty of the University of Buffalo in partial fulfillment of the requirements for the degree of

Synthesis of some tricyclic nucleosides related to the Y base of tRNA

“…Found: C, 47.1; , 5.00; N, 23.5. 5,6-Dihydro-6-hydroxy-10-oxo-3-/3-D-ribofuranosyl-l,2,4-triazino[2,3-a]purine (6). To a solution of glyoxal, prepared by refluxing glyoxal trimer (500 mg, 2.9 mmol) in 100 ml of H20 for 30 min, was slowly added 2 (500 mg, 1.68 mmol) in 100 ml of hot H20.…”

“…The interpretation receives support from the observation by Clark10 that ethyl pteridine-4-carboxylate readily forms a covalent hydrate in solution whereas its 6,7-dimethyl derivative is only slightly hydrated at equilibrium, and is confirmed by the pmr data discussed below. 5) and its covalent hydrate (6). For details of interpretation see text.…”

“…The position of hydration was shown by the pmr data cited above to occur across a C=N bond in the triazine ring; the assignment of the 5,6 double bond was made by analogy with recent work in which the 1,2,4-triazine system was shown to undergo covalent hydration at the analogous 4,5 double bond.13 Jv.v = 5.6 Hz J 6,7 = 3.0 Hz " Hs of purine listed under H2 for comparison. 6 Solvent D20. = Obscured by sugar OH protons.…”

“…Figure 1. Pmr spectrum in (CDa^SO of 10-oxo-3-/3-D-ribofuranosyl-l,2,4-triazmo[2,3-a]purine(5) and its covalent hydrate(6). For details of interpretation see text.…”

Ortho Esters

“…(31) Preparation of acyclic acyloxy ortho esters by the reaction of acid anhydrides with trialkyl orthoformates and trialkyl orthoacetates [198][199][200].…”