S = {'Hi B', 'Hi A', 'Hey guys D can''t come', 'Too Bad C', 'I Feel bad for D'};
names = {'A', 'B', 'C', 'D'};
namepattern = ['\<', strjoin(names,'\\>|\\<'), '\>'];
matched_names = regexp(S, namepattern, 'match');
The result will be a cell array the same size as S, with each entry containing a cell array of character vectors. The contained cell array will be empty if there are no name matches; it will contain a scalar cell array that contains a character vector if there is one match (the case you are expecting), and the contained cell array could contain multiple character vectors if multiple names were matched.
In the particular case where you are sure you only have at most one match, or you only want the first match if there are multiple matches, then you can use
matched_names = regexp(S, namepattern, 'match', 'once');
In that case, instead of matched_names being a cell array containing cell arrays, it would be a cell array directly containing character vectors
This code does not require that the names are single letters, and does not require that they are upper case. It will, however, only recognize them if they are isolated -- for example 'Too Bad C' it will detect that the 'B' in 'Bad' is followed by something that is word-like and so will not treat it as a match for the name 'B'. The code will consider digits and underscore to be word-like, so for example 'B_' and 'B3' would not be considered to match 'B' but 'B.' or 'B?' would be considered to match.
