Oxetanes formation

With aromatic carbonyls, oxetane formation appears to arise from the carbonyl triplet state, as evidenced by quenching studies. For example, benzaldehyde irradiated in the presence of cyclohexene yields products indicative of hydrogen abstraction reactions and an oxetane ... 

The reaction of carbonyl compounds to olefins often yields products difficult to obtain synthetically by other routes. The excellent yields obtainable under proper conditions make this reaction of definite preparative interest. Examples of some synthetic applications of oxetane formation follow ... 

For oxetane formation from formaldehyde and ethylene, we should consider the following four transition states and intermediates for the reaction<181) ... 

Yang has observed that cis-trans isomerization of 3-methyl-2-pentenes is accompanied by oxetane formation and concluded that intermediates such as (22) are common to both isomerization and oxetane formation/825 Deuterium isotope effects are also consistent with the involvement of this type of intermediate/83,845 ... 

The other photochemical reactions of simple carbonyls mentioned earlier in this chapter—type I cleavage (a-cleavage) and oxetane formation—will be discussed in Chapter 4. 

The Photochemistry of Simple Carbonyl Compounds Type I Cleavage and Oxetane Formation... 

In Chapter 3 we discussed two photochemical reactions characteristic of simple carbonyl compounds, namely type II cleavage and photoreduction. We saw that photoreduction appears to arise only from carbonyl triplet states, whereas type II cleavage often arises from both the excited singlet and triplet states. Each process was found to occur from discrete biradical intermediates. In this chapter we will discuss two other reactions observed in the photochemistry of carbonyls, type I cleavage and oxetane formation. 

Table 4.10. Reactivity of Various Aromatic Carbonyls toward Oxetane Formation and Photoreduction Compared to the Nature of the Lowest TripletiB3,9 Bm...

In a recent study of intramolecular oxetane formation in naphthoylnor-bornenes Sauers and Rousseau provided evidence that two distinct excited states are involved<99) ... 

Lange and Bosch<109) reported the interesting intramolecular oxetane formation shown below. Reduction with lithium aluminum hydride afforded m is-9-decalol (32%) ... 

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