trans alkene cyclization

[rentj]

i am wondering if i have a bromo substituent at the end of an unsaturated trans compound, where the other end is an aldehyde. if i put magnesium metal to make a grignard reagent of it, will it cyclize? the 'carbanion' will attack the aldehyde to form an alcohol, but what happens to the c=c double bond? in a cyclic molecule, the c=c bond has to be cis. if the initial molecule has a trans c=c bond, does the reaction occur? thank you.

[Laitive]

Very good question about the Grignard cyslization mechanism. Without isomerization from trans to cis, the reaction is unlikely to occur due to ring strain.

[floridarami]

Will the reaction occur? Yes, the Grignard will attack the aldehyde, forming an alcohol.
Will cyclization occur? It's unlikely if the starting alkene is trans because the chain's geometry doesn't favor cyclization.
What about the C=C bond? It generally remains unaltered unless specific conditions lead to addition or reduction across the double bond. The trans configuration will typically persist unless the reaction conditions promote isomerization or reduction.