Pentamethylene heterocycles

Since Eliel and Pietrusiewicz (142) have published a comprehensive review on l3C chemical shifts in saturated heterocycles, the discussion in the present report may be confined to a few basic features for the sake of completeness. It stands to reason that there is an electronegativity dependence of a-carbon chemical shifts. This was demonstrated by Lambert and co-workers (143) for a great variety of pentamethylene heterocycles, and holds also for positively charged species, such as X = (CH3)2N+, (CH3)2P+, CH3S +, Br+, and I+. The same is suggested by the good correlation of a-carbon chemical shifts in some heterocyclohexanes (143) and the a-SCS values in cyclohexanes with equatorial substituents (Figure 2)(114). 

The parent heterocycle is usually prepared by interaction of a sulfide and a pentamethylene derivative, as described above, and various alkyl and aryl substituted analogues are also... 

Numerous N-alkylnorcodeines have been prepared, and these can be nitrated, acetylated and chlorinated like codeine [361], Other N-substituted norcodeines have also been prepared [362-7], and of these N-aflylnorcodeine and other /3 y-unsaturated derivatives have an action antagonistic to that of morphine [364, 368], A dimolecular derivative results from the interaction of norcodeine and trans A2 3-l 4-dibromo-butene [369]. Spirocyclic quaternary salts such as [li] result from the treatment of norcodeine with pentamethylene iodide, o-xylyldibromide, and /3 /3 di-iododiethyl ether, and these suffer degradation in alkaline solution with fission of the codeine heterocyclic ring [370] (see Chap. VI). 

Pentadiene and dialkyl alanes give addition products from which only pentane is split off on hydrolysis (88). Nothing further is known yet about the constitution of these compounds, e.g., if aluminum heterocycles (6- or 5-ring compounds) are formed. Tris(3,3-dimethyl-pentamethylene) dialane is said to be formed from 3,3-dimethyl-l,4-pentadiene and di-isobutylaluminum hydride in 98% yield, even under forcing conditions at elevated temperatures (160°C). The compound distills at low pressures (b.p.io-t 132°-140°C) (212). 

---