Betylates. 2. The formation and high reactivity of alkyl [0]betylates

Abstract

. Can. J. Chem. 59,362 (1981). Unhindered primary alkyl N,N-dimethylsulfamates (1) react with methyl fluorosulfate to give the corresponding alkyl fluorosulfates (3) and the betaine, M~,&so,-(4), evidently by way of the intermediate alkyl [Olbetylate fluorosulfate (2); with certain other alkyl esters (1) products of substitution, elimination, and rearrangement are formed. The reaction not only provides a potentially useful route to simple alkyl fluorosulfates, but serves to demonstrate the powerful nucleofugality of the [Olbetylate group. To obtain a method for predicting the reactivity of [Olbetylates, we have compared substituent parameters with rate constants in four series of nucleophilic displacements involving esters of the general structure ROS02Z; correlation (of log k) with o* is mediocre but a new parameter, o : , with a "15% resonance" contribution as defined by Swain and Lupton, gives good to excellent agreement in the four reaction series. Evidence is presented for formation of the 7-norbornyl cation via the [Olbetylate from 7-norbornyl N,N-dimethylsulfamate and methyl fluorosulfate. Comparison with what is known of the reactivities of 7-norbornyl p-toluenesulfonate and trifluoromethanesulfonate esters serves to confirm that [0] betylates are among the most nucleofugal functions of which a derivative has been fully characterized.JAMES FREDERICK KING et TERESA MEE-LING LEE. Can. J. Chem. 59,362 (1981). Introduction more reactive than even the "super sulfonates". In the accompanying paper (1) we have reported Accordingly when we had determined that an aryl that phenyl N,N-dimethylsulfamate reacts with [Olbet~late could be prepared from an aryl N,Nmethyl fluorosulfate to yield the first example of an dimethylsulfamate, we quickly turned our attention isolable "[Qlbetylate" (i.e. trialkylammoniosul-to the corres~onding reaction of alkyl N,Nfate) ester.2 dimethylsulfamates. This paper describes our study of this reaction and our observation of the

Synthesis and Chemical Transformations of Fluorosulfates

“…Under their optimized reaction conditions, King and Lee reported the synthesis of alkyl fluorosulfates 34 in good yields from the reaction of alkyl N , N ‐diethyl sulfamates ( 90 ) with methyl fluorosulfates (Scheme ) …”

Attempts at Solvolytic Generation of Phenyl Cations

“…'Phenyl b e t~l a t e '~) (3) has recently been synthesized [30]; nucleophiles reacted with it either by attack at the S-or at the methyl-C-atoms [30]. Alkyl betylates, on the other hand, could not be isolated, but the reaction products indicated that they decompose yielding carbenium ions [31]. A comparison of the extremely short lifetime of alkyl betylates with that of alkyl trifluoromethanesulfonates (triflates) has led to the conclusion that the betylate is a better leaving group than triflate by a factor of more than lo5 [31], and thus with the exception of the diazonio group probably the best leaving group known.…”