Successful nucleophilic substitution at a methylene attached to the bridgehead (1-) position of the 2-azabicyclo[2.1.1]hexane ring system opens the way to construction of novel derivatives having a wider range of functional groups attached to the 1-position via a methylene "spacer" (including the beta-amino acid homologue of 2,4-methanoproline) and provides access to epibatidine analogues containing heterocyclic substituents and also to further homologation at the 1-position. Displacements with loss of a nucleofuge (e.g., loss of mesylate anion from the 1-mesyloxymethyl derivative) require thermal activation but proceed without the rearrangement initially anticipated in such a strained bicyclic ring system. A novel tricyclic carbamate intermediate 17 has been isolated; nucleophilic attack on 17 leads directly to the isolation of N-deprotected substitution products (with concomitant decarboxylation).

In immersed friction stir welding (FSW), the workpiece is completely immersed in the water environment during welding. The thermal modelling of immersed FSW is carried out using a three-dimensional heat transfer model. Friction stir welding experiments on aluminium AA8011 are carried out to find the temperature distributions in a workpiece in air and immersed state. K-type thermocouples are used to measure the temperature histories at different locations on the workpiece during FSW. A regression analysis is used to forecast the temperatures at the weldline experimentally. The temperature distribution at the weldline is also calculated using numerical simulation. The temperature distribution obtained using this experiment is in good agreement with the temperature distribution obtained using numerical simulation. The result indicates that peak temperature distribution area is significantly narrow, and thermal history showed that temperature rise and fall after FSW is sharp due to higher cooling rate in the presence of water. A comparison is also made between the temperature obtained in air and immersed FSW. It is also observed that the joint tensile strength of immersed FSW is higher than that of air FSW welded joint.

Potential nicotinic acetylcholine receptor (nAChR) ligands have been synthesized in which a methylisoxazole substituent is attached to the 1-position ( 26) of the 2-azabicyclo[2.1.1]hexane ring system or separated by "spacer" atoms ( 21 and 23). With ABT-594 as a model, a range of pyridine heterocycles have been attached to the 1-position via a -CH 2O- spacer ( 11, 14, and 6). The biological evaluation of target compounds showed there was no binding affinity at the alpha4beta2 and alpha3beta4 nAChR subtypes.

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