A Practical Synthesis of Mixed Allyl and Allenesulfinates

Abstract

A new, general, and efficient method for the preparation of mixed sulfoxylates (ROSOR¢) by treatment of symmetrical dialkoxy disulfides (ROSSOR) with alcohols at room temperature has been found. Subsequent spontaneous [2,3]-sigmatropic rearrangements of mixed sulfoxylates such as alkyl allyl and alkyl propargyl sulfoxylates afford mixed alkyl allyl and alkyl allenesulfinates in good yield. The latter are not readily available by other routes.The highly efficient and stereoselective [2,3]-sigmatropic rearrangements of allylic and propargylic sulfenates and sulfinates, discovered by us more than three decades ago 1 have found extensive application in organic synthesis since their publication. 2,3 In one such application from our own laboratory, a combination of two such rearrangements was used to prepare bis(g,g-dimethylallenyl) sulfone. 4 As shown in Scheme 1, the latter is readily obtained by a double [2,3]-sigmatropic rearrangement of bis-(a,adimethylpropargyl) sulfoxylate. Furthermore, this sulfone underwent a facile and quantitative cyclization via a diradical intermediate on heating to a thiophene 1,1-dioxide derivative (Scheme 1). 4 More recently, this cyclization has also been used as a model for the design of a new class of DNA cleaving molecules which could mimic the biological activity of the naturally occurring enediynes. 5,6 Notwithstanding the previously reported unsuccessful attempts to prepare allylic and propargylic dialkoxy disulfides, 7 we have recently succeeded in the preparation of a variety of such esters in good to high yields. 8,9 Testing the reactivity of allylic dialkoxy disulfides 1a-f we have found that on heating in refluxing acetonitrile solution, these esters readily undergo a double [2,3]-sigmatropic rearrangement to the expected vic-disulfoxides 3a-f, which rearrange further to the corresponding thiosulfonates 4a-f due to their well known instability (Scheme 2). 10 Unlike the allylic esters, the dipropargylic dialkoxy disulfides 5a-d afforded novel 6,7-dithiabicyclo[3.1.1]heptane-2-one-6-oxide derivatives 6a-d via an unprecedented sequence of three [2,3]-and one [3,3]-sigmatropic shifts, followed by an intramolecular [2+2] cycloaddition (Equation 1). 9 The products are structurally related to the novel zwiebelanes, recently isolated by Block from freshly cut onion. 11 Equation 1As previously pointed out, 8 our first attempts to test the reactivity of the allylic dialkoxy disulfides at room temperature were rather disappointing, due to the formation of allylic sulfinates resulting from [2,3]-sigmatropic rearrangement of the corresponding sulfoxylates. Similar disturbing products were also observed for some of the propargylic dialkoxy disulfides. For example, when propargyl dialkoxy disulfide is dissolved in chloroform and Scheme 1Downloaded by: University of Florida. Copyrighted material.

Facile Syntheses of Allylic Allenethiosulfinates and -sulfonates, and of β-Iodo α,β-Unsaturated γ-Sultines

“…To obtain a γ,γ-dialkylsultine such as β-iodo α,β-unsaturated γ,γ-dimethyl-γ-sultine 12 in quantitative yield it was most convenient to react the readily available 2-methylbut-3-yn-2-yl 3-methylbuta-1,2-diene 1-sulfinate 11 with I 2 in CH 2 Cl 2 solution for 1 min at room temperature (Scheme ). To obtain the γ-monoalkyl or the γ-unsubstituted sultines, it was found advantageous to react the iodine with the appropriate methyl allenesulfinate 15 , prepared as shown in Scheme . The terminally unsubstituted, and therefore less nucleophilic, β,γ-double bond of the allene 15b required a much longer reaction time (20 h compared to only 1 min for 15a ).…”