Haines

Since 1,2- to 1,6-difunctional opengeneral procedures (see chapter 1), it is useful to consider them as possible starting materials for syntheses of three- to seven-membered heterocycies 1,2-heterocycles can be made from 1,2-difunctional compounds, e.g. olefins or dibromides 1,3-difunctional compounds, e.g. 1,3-dibromides or 1,3-dioxo compounds, can be converted into 1,3-heterocycles etc. 

The hydroxyl groups of glucose (and, of course, other saccharides) must be regio- and stereo-selectively attacked, if this most abundant natural carbon compound is to be used as starting material. We shall first show with a few selected examples, how this can be achieved (A.H. Haines, 1976 J. Lehmann, 1976 L. Hough, 1979). 

R. W. Haines, HTAC System Design Handbook, TAB Books, Blue Ridge Summit, Pa., 1988. 

R. W. Haines, Control Systems for Heating Ventilating and Air Conditioning, Van Nostrand-Reinhold, New York, 4th ed., 1987. 

An interesting variant in which nucleophilic aromatic substitution is carried out on the crown nucleus rather than using the crown as nucleophile was reported by Haines . In this approach, hexafluorobenzene was stirred in 1,2-dimethoxyethane at room temperature with pentaethylene glycol and sodium hydride. A double nucleophilic aromatic substitution occurred affording 2, 3, 4 ,5 -tetrafluorobenzo-15-crown-5 as an oil in 38% yield. The reaction is illustrated below. 

Haines and Karntiang later adopted a somewhat more symmetrical approach in the synthesis of glycerol-based cryptands when they utilized the six-membered benzylidene derivative of glyceroP. Details of the synthesis described in Eq. (8.8), above, are also presented in this paper. The symmetrical approach is quite similar to that described in Eq. (8.8), and is outlined below in Eq. (8.9). 

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